ATT&CK explorer

Adversaries may reveal credentials of accounts that have disabled Kerberos preauthentication by Password Cracking Kerberos messages.(Citation: Harmj0y Roasting AS-REPs Jan 2017) Preauthentication offers protection against offline Password Cracking. When enabled, a user requesting access to a resource initiates communication with the Domain Controller (DC) by sending an Authentication Server Request (AS-REQ) message with a timestamp that is encrypted with the hash of their password. If and only if the DC is able to successfully decrypt the timestamp with the hash of the user’s password, it will then send an Authentication Server Response (AS-REP) message that contains the Ticket Granting Ticket (TGT) to the user. Part of the AS-REP message is signed with the user’s password.(Citation: Microsoft Kerberos Preauth 2014) For each account found without preauthentication, an adversary may send an AS-REQ message without the encrypted timestamp and receive an AS-REP message with TGT data which may be encrypted with an insecure algorithm such as RC4. The recovered encrypted data may be vulnerable to offline Password Cracking attacks similarly to Kerberoasting and expose plaintext credentials. (Citation: Harmj0y Roasting AS-REPs Jan 2017)(Citation: Stealthbits Cracking AS-REP Roasting Jun 2019) An account registered to a domain, with or without special privileges, can be abused to list all domain accounts that have preauthentication disabled by utilizing Windows tools like PowerShell with an LDAP filter. Alternatively, the adversary may send an AS-REQ message for each user. If the DC responds without errors, the account does not require preauthentication and the AS-REP message will already contain the encrypted data. (Citation: Harmj0y Roasting AS-REPs Jan 2017)(Citation: Stealthbits Cracking AS-REP Roasting Jun 2019) Cracked hashes may enable Persistence, Privilege Escalation, and Lateral Movement via access to Valid Accounts.(Citation: SANS Attacking Kerberos Nov 2014)

Adversaries may attempt to steal Kerberos tickets stored in credential cache files (or ccache). These files are used for short term storage of a user's active session credentials. The ccache file is created upon user authentication and allows for access to multiple services without the user having to re-enter credentials. The <code>/etc/krb5.conf</code> configuration file and the <code>KRB5CCNAME</code> environment variable are used to set the storage location for ccache entries. On Linux, credentials are typically stored in the `/tmp` directory with a naming format of `krb5cc_%UID%` or `krb5.ccache`. On macOS, ccache entries are stored by default in memory with an `API:{uuid}` naming scheme. Typically, users interact with ticket storage using <code>kinit</code>, which obtains a Ticket-Granting-Ticket (TGT) for the principal; <code>klist</code>, which lists obtained tickets currently held in the credentials cache; and other built-in binaries.(Citation: Kerberos GNU/Linux)(Citation: Binary Defense Kerberos Linux) Adversaries can collect tickets from ccache files stored on disk and authenticate as the current user without their password to perform Pass the Ticket attacks. Adversaries can also use these tickets to impersonate legitimate users with elevated privileges to perform Privilege Escalation. Tools like Kekeo can also be used by adversaries to convert ccache files to Windows format for further Lateral Movement. On macOS, adversaries may use open-source tools or the Kerberos framework to interact with ccache files and extract TGTs or Service Tickets via lower-level APIs.(Citation: SpectorOps Bifrost Kerberos macOS 2019)(Citation: Linux Kerberos Tickets)(Citation: Brining MimiKatz to Unix)(Citation: Kekeo)

Adversaries may abuse inter-process communication (IPC) mechanisms for local code or command execution. IPC is typically used by processes to share data, communicate with each other, or synchronize execution. IPC is also commonly used to avoid situations such as deadlocks, which occurs when processes are stuck in a cyclic waiting pattern. Adversaries may abuse IPC to execute arbitrary code or commands. IPC mechanisms may differ depending on OS, but typically exists in a form accessible through programming languages/libraries or native interfaces such as Windows Dynamic Data Exchange or Component Object Model. Linux environments support several different IPC mechanisms, two of which being sockets and pipes.(Citation: Linux IPC) Higher level execution mediums, such as those of Command and Scripting Interpreters, may also leverage underlying IPC mechanisms. Adversaries may also use Remote Services such as Distributed Component Object Model to facilitate remote IPC execution.(Citation: Fireeye Hunting COM June 2019)

Adversaries may use the Windows Component Object Model (COM) for local code execution. COM is an inter-process communication (IPC) component of the native Windows application programming interface (API) that enables interaction between software objects, or executable code that implements one or more interfaces.(Citation: Fireeye Hunting COM June 2019) Through COM, a client object can call methods of server objects, which are typically binary Dynamic Link Libraries (DLL) or executables (EXE).(Citation: Microsoft COM) Remote COM execution is facilitated by Remote Services such as Distributed Component Object Model (DCOM).(Citation: Fireeye Hunting COM June 2019) Various COM interfaces are exposed that can be abused to invoke arbitrary execution via a variety of programming languages such as C, C++, Java, and Visual Basic.(Citation: Microsoft COM) Specific COM objects also exist to directly perform functions beyond code execution, such as creating a Scheduled Task/Job, fileless download/execution, and other adversary behaviors related to privilege escalation and persistence.(Citation: Fireeye Hunting COM June 2019)(Citation: ProjectZero File Write EoP Apr 2018)

Adversaries may use Windows Dynamic Data Exchange (DDE) to execute arbitrary commands. DDE is a client-server protocol for one-time and/or continuous inter-process communication (IPC) between applications. Once a link is established, applications can autonomously exchange transactions consisting of strings, warm data links (notifications when a data item changes), hot data links (duplications of changes to a data item), and requests for command execution. Object Linking and Embedding (OLE), or the ability to link data between documents, was originally implemented through DDE. Despite being superseded by Component Object Model, DDE may be enabled in Windows 10 and most of Microsoft Office 2016 via Registry keys.(Citation: BleepingComputer DDE Disabled in Word Dec 2017)(Citation: Microsoft ADV170021 Dec 2017)(Citation: Microsoft DDE Advisory Nov 2017) Microsoft Office documents can be poisoned with DDE commands, directly or through embedded files, and used to deliver execution via Phishing campaigns or hosted Web content, avoiding the use of Visual Basic for Applications (VBA) macros.(Citation: SensePost PS DDE May 2016)(Citation: Kettle CSV DDE Aug 2014)(Citation: Enigma Reviving DDE Jan 2018)(Citation: SensePost MacroLess DDE Oct 2017) Similarly, adversaries may infect payloads to execute applications and/or commands on a victim device by way of embedding DDE formulas within a CSV file intended to be opened through a Windows spreadsheet program.(Citation: OWASP CSV Injection)(Citation: CSV Excel Macro Injection ) DDE could also be leveraged by an adversary operating on a compromised machine who does not have direct access to a Command and Scripting Interpreter. DDE execution can be invoked remotely via Remote Services such as Distributed Component Object Model (DCOM).(Citation: Fireeye Hunting COM June 2019)

Adversaries can provide malicious content to an XPC service daemon for local code execution. macOS uses XPC services for basic inter-process communication between various processes, such as between the XPC Service daemon and third-party application privileged helper tools. Applications can send messages to the XPC Service daemon, which runs as root, using the low-level XPC Service <code>C API</code> or the high level <code>NSXPCConnection API</code> in order to handle tasks that require elevated privileges (such as network connections). Applications are responsible for providing the protocol definition which serves as a blueprint of the XPC services. Developers typically use XPC Services to provide applications stability and privilege separation between the application client and the daemon.(Citation: creatingXPCservices)(Citation: Designing Daemons Apple Dev) Adversaries can abuse XPC services to execute malicious content. Requests for malicious execution can be passed through the application's XPC Services handler.(Citation: CVMServer Vuln)(Citation: Learn XPC Exploitation) This may also include identifying and abusing improper XPC client validation and/or poor sanitization of input parameters to conduct Exploitation for Privilege Escalation.

An adversary may compress and/or encrypt data that is collected prior to exfiltration. Compressing the data can help to obfuscate the collected data and minimize the amount of data sent over the network.(Citation: DOJ GRU Indictment Jul 2018) Encryption can be used to hide information that is being exfiltrated from detection or make exfiltration less conspicuous upon inspection by a defender. Both compression and encryption are done prior to exfiltration, and can be performed using a utility, 3rd party library, or custom method.

Adversaries may use utilities to compress and/or encrypt collected data prior to exfiltration. Many utilities include functionalities to compress, encrypt, or otherwise package data into a format that is easier/more secure to transport. Adversaries may abuse various utilities to compress or encrypt data before exfiltration. Some third party utilities may be preinstalled, such as <code>tar</code> on Linux and macOS or <code>zip</code> on Windows systems. On Windows, <code>diantz</code> or <code> makecab</code> may be used to package collected files into a cabinet (.cab) file. <code>diantz</code> may also be used to download and compress files from remote locations (i.e. Remote Data Staging).(Citation: diantz.exe_lolbas) <code>xcopy</code> on Windows can copy files and directories with a variety of options. Additionally, adversaries may use certutil to Base64 encode collected data before exfiltration. Adversaries may use also third party utilities, such as 7-Zip, WinRAR, and WinZip, to perform similar activities.(Citation: 7zip Homepage)(Citation: WinRAR Homepage)(Citation: WinZip Homepage)

An adversary may compress or encrypt data that is collected prior to exfiltration using 3rd party libraries. Many libraries exist that can archive data, including Python rarfile (Citation: PyPI RAR), libzip (Citation: libzip), and zlib (Citation: Zlib Github). Most libraries include functionality to encrypt and/or compress data. Some archival libraries are preinstalled on systems, such as bzip2 on macOS and Linux, and zip on Windows. Note that the libraries are different from the utilities. The libraries can be linked against when compiling, while the utilities require spawning a subshell, or a similar execution mechanism.

An adversary may compress or encrypt data that is collected prior to exfiltration using a custom method. Adversaries may choose to use custom archival methods, such as encryption with XOR or stream ciphers implemented with no external library or utility references. Custom implementations of well-known compression algorithms have also been used.(Citation: ESET Sednit Part 2)

Adversaries may wipe or corrupt raw disk data on specific systems or in large numbers in a network to interrupt availability to system and network resources. With direct write access to a disk, adversaries may attempt to overwrite portions of disk data. Adversaries may opt to wipe arbitrary portions of disk data and/or wipe disk structures like the master boot record (MBR). A complete wipe of all disk sectors may be attempted. To maximize impact on the target organization in operations where network-wide availability interruption is the goal, malware used for wiping disks may have worm-like features to propagate across a network by leveraging additional techniques like Valid Accounts, OS Credential Dumping, and SMB/Windows Admin Shares.(Citation: Novetta Blockbuster Destructive Malware) On network devices, adversaries may wipe configuration files and other data from the device using Network Device CLI commands such as `erase`.(Citation: erase_cmd_cisco)

Adversaries may erase the contents of storage devices on specific systems or in large numbers in a network to interrupt availability to system and network resources. Adversaries may partially or completely overwrite the contents of a storage device rendering the data irrecoverable through the storage interface.(Citation: Novetta Blockbuster)(Citation: Novetta Blockbuster Destructive Malware)(Citation: DOJ Lazarus Sony 2018) Instead of wiping specific disk structures or files, adversaries with destructive intent may wipe arbitrary portions of disk content. To wipe disk content, adversaries may acquire direct access to the hard drive in order to overwrite arbitrarily sized portions of disk with random data.(Citation: Novetta Blockbuster Destructive Malware) Adversaries have also been observed leveraging third-party drivers like RawDisk to directly access disk content.(Citation: Novetta Blockbuster)(Citation: Novetta Blockbuster Destructive Malware) This behavior is distinct from Data Destruction because sections of the disk are erased instead of individual files. To maximize impact on the target organization in operations where network-wide availability interruption is the goal, malware used for wiping disk content may have worm-like features to propagate across a network by leveraging additional techniques like Valid Accounts, OS Credential Dumping, and SMB/Windows Admin Shares.(Citation: Novetta Blockbuster Destructive Malware)

Adversaries may corrupt or wipe the disk data structures on a hard drive necessary to boot a system; targeting specific critical systems or in large numbers in a network to interrupt availability to system and network resources. Adversaries may attempt to render the system unable to boot by overwriting critical data located in structures such as the master boot record (MBR) or partition table.(Citation: Symantec Shamoon 2012)(Citation: FireEye Shamoon Nov 2016)(Citation: Palo Alto Shamoon Nov 2016)(Citation: Kaspersky StoneDrill 2017)(Citation: Unit 42 Shamoon3 2018) The data contained in disk structures may include the initial executable code for loading an operating system or the location of the file system partitions on disk. If this information is not present, the computer will not be able to load an operating system during the boot process, leaving the computer unavailable. Disk Structure Wipe may be performed in isolation, or along with Disk Content Wipe if all sectors of a disk are wiped. On a network devices, adversaries may reformat the file system using Network Device CLI commands such as `format`.(Citation: format_cmd_cisco) To maximize impact on the target organization, malware designed for destroying disk structures may have worm-like features to propagate across a network by leveraging other techniques like Valid Accounts, OS Credential Dumping, and SMB/Windows Admin Shares.(Citation: Symantec Shamoon 2012)(Citation: FireEye Shamoon Nov 2016)(Citation: Palo Alto Shamoon Nov 2016)(Citation: Kaspersky StoneDrill 2017)

Adversaries may maliciously modify components of a victim environment in order to hinder or disable defensive mechanisms. This not only involves impairing preventative defenses, such as firewalls and anti-virus, but also detection capabilities that defenders can use to audit activity and identify malicious behavior. This may also span both native defenses as well as supplemental capabilities installed by users and administrators. Adversaries may also impair routine operations that contribute to defensive hygiene, such as blocking users from logging out, preventing a system from shutting down, or disabling or modifying the update process. Adversaries could also target event aggregation and analysis mechanisms, or otherwise disrupt these procedures by altering other system components. These restrictions can further enable malicious operations as well as the continued propagation of incidents.(Citation: Google Cloud Mandiant UNC3886 2024)(Citation: Emotet shutdown)

Adversaries may modify and/or disable security tools to avoid possible detection of their malware/tools and activities. This may take many forms, such as killing security software processes or services, modifying / deleting Registry keys or configuration files so that tools do not operate properly, or other methods to interfere with security tools scanning or reporting information. Adversaries may also disable updates to prevent the latest security patches from reaching tools on victim systems.(Citation: SCADAfence_ransomware) Adversaries may trigger a denial-of-service attack via legitimate system processes. It has been previously observed that the Windows Time Travel Debugging (TTD) monitor driver can be used to initiate a debugging session for a security tool (e.g., an EDR) and render the tool non-functional. By hooking the debugger into the EDR process, all child processes from the EDR will be automatically suspended. The attacker can terminate any EDR helper processes (unprotected by Windows Protected Process Light) by abusing the Process Explorer driver. In combination this will halt any attempt to restart services and cause the tool to crash.(Citation: Cocomazzi FIN7 Reboot) Adversaries may also tamper with artifacts deployed and utilized by security tools. Security tools may make dynamic changes to system components in order to maintain visibility into specific events. For example, security products may load their own modules and/or modify those loaded by processes to facilitate data collection. Similar to Indicator Blocking, adversaries may unhook or otherwise modify these features added by tools (especially those that exist in userland or are otherwise potentially accessible to adversaries) to avoid detection.(Citation: OutFlank System Calls)(Citation: MDSec System Calls) For example, adversaries may abuse the Windows process mitigation policy to block certain endpoint detection and response (EDR) products from loading their user-mode code via DLLs. By spawning a process with the PROCESS_CREATION_MITIGATION_POLICY_BLOCK_NON_MICROSOFT_BINARIES_ALWAYS_ON attribute using API calls like UpdateProcThreadAttribute, adversaries may evade detection by endpoint security solutions that rely on DLLs that are not signed by Microsoft. Alternatively, they may add new directories to an EDR tool’s exclusion list, enabling them to hide malicious files via File/Path Exclusions.(Citation: BlackBerry WhisperGate 2022)(Citation: Google Cloud Threat Intelligence FIN13 2021) Adversaries may also focus on specific applications such as Sysmon. For example, the “Start” and “Enable” values in <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-Microsoft-Windows-Sysmon-Operational</code> may be modified to tamper with and potentially disable Sysmon logging.(Citation: disable_win_evt_logging) On network devices, adversaries may attempt to skip digital signature verification checks by altering startup configuration files and effectively disabling firmware verification that typically occurs at boot.(Citation: Fortinet Zero-Day and Custom Malware Used by Suspected Chinese Actor in Espionage Operation)(Citation: Analysis of FG-IR-22-369) In cloud environments, tools disabled by adversaries may include cloud monitoring agents that report back to services such as AWS CloudWatch or Google Cloud Monitor. Furthermore, although defensive tools may have anti-tampering mechanisms, adversaries may abuse tools such as legitimate rootkit removal kits to impair and/or disable these tools.(Citation: chasing_avaddon_ransomware)(Citation: dharma_ransomware)(Citation: demystifying_ryuk)(Citation: doppelpaymer_crowdstrike) For example, adversaries have used tools such as GMER to find and shut down hidden processes and antivirus software on infected systems.(Citation: demystifying_ryuk) Additionally, adversaries may exploit legitimate drivers from anti-virus software to gain access to kernel space (i.e. Exploitation for Privilege Escalation), which may lead to bypassing anti-tampering features.(Citation: avoslocker_ransomware)

Adversaries may disable Windows event logging to limit data that can be leveraged for detections and audits. Windows event logs record user and system activity such as login attempts, process creation, and much more.(Citation: Windows Log Events) This data is used by security tools and analysts to generate detections. The EventLog service maintains event logs from various system components and applications.(Citation: EventLog_Core_Technologies) By default, the service automatically starts when a system powers on. An audit policy, maintained by the Local Security Policy (secpol.msc), defines which system events the EventLog service logs. Security audit policy settings can be changed by running secpol.msc, then navigating to <code>Security Settings\Local Policies\Audit Policy</code> for basic audit policy settings or <code>Security Settings\Advanced Audit Policy Configuration</code> for advanced audit policy settings.(Citation: Audit_Policy_Microsoft)(Citation: Advanced_sec_audit_policy_settings) <code>auditpol.exe</code> may also be used to set audit policies.(Citation: auditpol) Adversaries may target system-wide logging or just that of a particular application. For example, the Windows EventLog service may be disabled using the <code>Set-Service -Name EventLog -Status Stopped</code> or <code>sc config eventlog start=disabled</code> commands (followed by manually stopping the service using <code>Stop-Service -Name EventLog</code>).(Citation: Disable_Win_Event_Logging)(Citation: disable_win_evt_logging) Additionally, the service may be disabled by modifying the “Start” value in <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog</code> then restarting the system for the change to take effect.(Citation: disable_win_evt_logging) There are several ways to disable the EventLog service via registry key modification. First, without Administrator privileges, adversaries may modify the "Start" value in the key <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-Security</code>, then reboot the system to disable the Security EventLog.(Citation: winser19_file_overwrite_bug_twitter) Second, with Administrator privilege, adversaries may modify the same values in <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-System</code> and <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\WMI\Autologger\EventLog-Application</code> to disable the entire EventLog.(Citation: disable_win_evt_logging) Additionally, adversaries may use <code>auditpol</code> and its sub-commands in a command prompt to disable auditing or clear the audit policy. To enable or disable a specified setting or audit category, adversaries may use the <code>/success</code> or <code>/failure</code> parameters. For example, <code>auditpol /set /category:”Account Logon” /success:disable /failure:disable</code> turns off auditing for the Account Logon category.(Citation: auditpol.exe_STRONTIC)(Citation: T1562.002_redcanaryco) To clear the audit policy, adversaries may run the following lines: <code>auditpol /clear /y</code> or <code>auditpol /remove /allusers</code>.(Citation: T1562.002_redcanaryco) By disabling Windows event logging, adversaries can operate while leaving less evidence of a compromise behind.

Adversaries may impair command history logging to hide commands they run on a compromised system. Various command interpreters keep track of the commands users type in their terminal so that users can retrace what they've done. On Linux and macOS, command history is tracked in a file pointed to by the environment variable <code>HISTFILE</code>. When a user logs off a system, this information is flushed to a file in the user's home directory called <code>~/.bash_history</code>. The <code>HISTCONTROL</code> environment variable keeps track of what should be saved by the <code>history</code> command and eventually into the <code>~/.bash_history</code> file when a user logs out. <code>HISTCONTROL</code> does not exist by default on macOS, but can be set by the user and will be respected. The `HISTFILE` environment variable is also used in some ESXi systems.(Citation: Google Cloud Threat Intelligence ESXi VIBs 2022) Adversaries may clear the history environment variable (<code>unset HISTFILE</code>) or set the command history size to zero (<code>export HISTFILESIZE=0</code>) to prevent logging of commands. Additionally, <code>HISTCONTROL</code> can be configured to ignore commands that start with a space by simply setting it to "ignorespace". <code>HISTCONTROL</code> can also be set to ignore duplicate commands by setting it to "ignoredups". In some Linux systems, this is set by default to "ignoreboth" which covers both of the previous examples. This means that “ ls” will not be saved, but “ls” would be saved by history. Adversaries can abuse this to operate without leaving traces by simply prepending a space to all of their terminal commands. On Windows systems, the <code>PSReadLine</code> module tracks commands used in all PowerShell sessions and writes them to a file (<code>$env:APPDATA\Microsoft\Windows\PowerShell\PSReadLine\ConsoleHost_history.txt</code> by default). Adversaries may change where these logs are saved using <code>Set-PSReadLineOption -HistorySavePath {File Path}</code>. This will cause <code>ConsoleHost_history.txt</code> to stop receiving logs. Additionally, it is possible to turn off logging to this file using the PowerShell command <code>Set-PSReadlineOption -HistorySaveStyle SaveNothing</code>.(Citation: Microsoft PowerShell Command History)(Citation: Sophos PowerShell command audit)(Citation: Sophos PowerShell Command History Forensics) Adversaries may also leverage a Network Device CLI on network devices to disable historical command logging (e.g. <code>no logging</code>).

Adversaries may disable or modify system firewalls in order to bypass controls limiting network usage. Changes could be disabling the entire mechanism as well as adding, deleting, or modifying particular rules. This can be done numerous ways depending on the operating system, including via command-line, editing Windows Registry keys, and Windows Control Panel. Modifying or disabling a system firewall may enable adversary C2 communications, lateral movement, and/or data exfiltration that would otherwise not be allowed. For example, adversaries may add a new firewall rule for a well-known protocol (such as RDP) using a non-traditional and potentially less securitized port (i.e. Non-Standard Port).(Citation: change_rdp_port_conti) Adversaries may also modify host networking settings that indirectly manipulate system firewalls, such as interface bandwidth or network connection request thresholds.(Citation: Huntress BlackCat) Settings related to enabling abuse of various Remote Services may also indirectly modify firewall rules. In ESXi, firewall rules may be modified directly via the esxcli command line interface (e.g., via `esxcli network firewall set`) or via the vCenter user interface.(Citation: Trellix Rnasomhouse 2024)(Citation: Broadcom ESXi Firewall)

An adversary may attempt to block indicators or events typically captured by sensors from being gathered and analyzed. This could include maliciously redirecting(Citation: Microsoft Lamin Sept 2017) or even disabling host-based sensors, such as Event Tracing for Windows (ETW)(Citation: Microsoft About Event Tracing 2018), by tampering settings that control the collection and flow of event telemetry.(Citation: Medium Event Tracing Tampering 2018) These settings may be stored on the system in configuration files and/or in the Registry as well as being accessible via administrative utilities such as PowerShell or Windows Management Instrumentation. For example, adversaries may modify the `File` value in <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\Security</code> to hide their malicious actions in a new or different .evtx log file. This action does not require a system reboot and takes effect immediately.(Citation: disable_win_evt_logging) ETW interruption can be achieved multiple ways, however most directly by defining conditions using the PowerShell <code>Set-EtwTraceProvider</code> cmdlet or by interfacing directly with the Registry to make alterations. In the case of network-based reporting of indicators, an adversary may block traffic associated with reporting to prevent central analysis. This may be accomplished by many means, such as stopping a local process responsible for forwarding telemetry and/or creating a host-based firewall rule to block traffic to specific hosts responsible for aggregating events, such as security information and event management (SIEM) products. In Linux environments, adversaries may disable or reconfigure log processing tools such as syslog or nxlog to inhibit detection and monitoring capabilities to facilitate follow on behaviors. (Citation: LemonDuck) ESXi also leverages syslog, which can be reconfigured via commands such as `esxcli system syslog config set` and `esxcli system syslog config reload`.(Citation: Google Cloud Threat Intelligence ESXi VIBs 2022)(Citation: Broadcom Configuring syslog on ESXi)

Adversaries may disable or modify a firewall within a cloud environment to bypass controls that limit access to cloud resources. Cloud firewalls are separate from system firewalls that are described in Disable or Modify System Firewall. Cloud environments typically utilize restrictive security groups and firewall rules that only allow network activity from trusted IP addresses via expected ports and protocols. An adversary with appropriate permissions may introduce new firewall rules or policies to allow access into a victim cloud environment and/or move laterally from the cloud control plane to the data plane. For example, an adversary may use a script or utility that creates new ingress rules in existing security groups (or creates new security groups entirely) to allow any TCP/IP connectivity to a cloud-hosted instance.(Citation: Palo Alto Unit 42 Compromised Cloud Compute Credentials 2022) They may also remove networking limitations to support traffic associated with malicious activity (such as cryptomining).(Citation: Expel IO Evil in AWS)(Citation: Palo Alto Unit 42 Compromised Cloud Compute Credentials 2022) Modifying or disabling a cloud firewall may enable adversary C2 communications, lateral movement, and/or data exfiltration that would otherwise not be allowed. It may also be used to open up resources for Brute Force or Endpoint Denial of Service.

An adversary may disable or modify cloud logging capabilities and integrations to limit what data is collected on their activities and avoid detection. Cloud environments allow for collection and analysis of audit and application logs that provide insight into what activities a user does within the environment. If an adversary has sufficient permissions, they can disable or modify logging to avoid detection of their activities. For example, in AWS an adversary may disable CloudWatch/CloudTrail integrations prior to conducting further malicious activity.(Citation: Following the CloudTrail: Generating strong AWS security signals with Sumo Logic) They may alternatively tamper with logging functionality – for example, by removing any associated SNS topics, disabling multi-region logging, or disabling settings that validate and/or encrypt log files.(Citation: AWS Update Trail)(Citation: Pacu Detection Disruption Module) In Office 365, an adversary may disable logging on mail collection activities for specific users by using the `Set-MailboxAuditBypassAssociation` cmdlet, by disabling M365 Advanced Auditing for the user, or by downgrading the user’s license from an Enterprise E5 to an Enterprise E3 license.(Citation: Dark Reading Microsoft 365 Attacks 2021)

Adversaries may abuse Windows safe mode to disable endpoint defenses. Safe mode starts up the Windows operating system with a limited set of drivers and services. Third-party security software such as endpoint detection and response (EDR) tools may not start after booting Windows in safe mode. There are two versions of safe mode: Safe Mode and Safe Mode with Networking. It is possible to start additional services after a safe mode boot.(Citation: Microsoft Safe Mode)(Citation: Sophos Snatch Ransomware 2019) Adversaries may abuse safe mode to disable endpoint defenses that may not start with a limited boot. Hosts can be forced into safe mode after the next reboot via modifications to Boot Configuration Data (BCD) stores, which are files that manage boot application settings.(Citation: Microsoft bcdedit 2021) Adversaries may also add their malicious applications to the list of minimal services that start in safe mode by modifying relevant Registry values (i.e. Modify Registry). Malicious Component Object Model (COM) objects may also be registered and loaded in safe mode.(Citation: Sophos Snatch Ransomware 2019)(Citation: CyberArk Labs Safe Mode 2016)(Citation: Cybereason Nocturnus MedusaLocker 2020)(Citation: BleepingComputer REvil 2021)

Adversaries may downgrade or use a version of system features that may be outdated, vulnerable, and/or does not support updated security controls. Downgrade attacks typically take advantage of a system’s backward compatibility to force it into less secure modes of operation. Adversaries may downgrade and use various less-secure versions of features of a system, such as Command and Scripting Interpreters or even network protocols that can be abused to enable Adversary-in-the-Middle or Network Sniffing.(Citation: Praetorian TLS Downgrade Attack 2014) For example, PowerShell versions 5+ includes Script Block Logging (SBL), which can record executed script content. However, adversaries may attempt to execute a previous version of PowerShell that does not support SBL with the intent to Impair Defenses while running malicious scripts that may have otherwise been detected.(Citation: CrowdStrike BGH Ransomware 2021)(Citation: Mandiant BYOL 2018)(Citation: att_def_ps_logging) Adversaries may similarly target network traffic to downgrade from an encrypted HTTPS connection to an unsecured HTTP connection that exposes network data in clear text.(Citation: Targeted SSL Stripping Attacks Are Real)(Citation: Crowdstrike Downgrade) On Windows systems, adversaries may downgrade the boot manager to a vulnerable version that bypasses Secure Boot, granting the ability to disable various operating system security mechanisms.(Citation: SafeBreach)

Adversaries may spoof security alerting from tools, presenting false evidence to impair defenders’ awareness of malicious activity.(Citation: BlackBasta) Messages produced by defensive tools contain information about potential security events as well as the functioning status of security software and the system. Security reporting messages are important for monitoring the normal operation of a system and identifying important events that can signal a security incident. Rather than or in addition to Indicator Blocking, an adversary can spoof positive affirmations that security tools are continuing to function even after legitimate security tools have been disabled (e.g., Disable or Modify Tools). An adversary can also present a “healthy” system status even after infection. This can be abused to enable further malicious activity by delaying defender responses. For example, adversaries may show a fake Windows Security GUI and tray icon with a “healthy” system status after Windows Defender and other system tools have been disabled.(Citation: BlackBasta)

Adversaries may disable or modify the Linux audit system to hide malicious activity and avoid detection. Linux admins use the Linux Audit system to track security-relevant information on a system. The Linux Audit system operates at the kernel-level and maintains event logs on application and system activity such as process, network, file, and login events based on pre-configured rules. Often referred to as `auditd`, this is the name of the daemon used to write events to disk and is governed by the parameters set in the `audit.conf` configuration file. Two primary ways to configure the log generation rules are through the command line `auditctl` utility and the file `/etc/audit/audit.rules`, containing a sequence of `auditctl` commands loaded at boot time.(Citation: Red Hat System Auditing)(Citation: IzyKnows auditd threat detection 2022) With root privileges, adversaries may be able to ensure their activity is not logged through disabling the Audit system service, editing the configuration/rule files, or by hooking the Audit system library functions. Using the command line, adversaries can disable the Audit system service through killing processes associated with `auditd` daemon or use `systemctl` to stop the Audit service. Adversaries can also hook Audit system functions to disable logging or modify the rules contained in the `/etc/audit/audit.rules` or `audit.conf` files to ignore malicious activity.(Citation: Trustwave Honeypot SkidMap 2023)(Citation: ESET Ebury Feb 2014)

Adversaries may disable network device-based firewall mechanisms entirely or add, delete, or modify particular rules in order to bypass controls limiting network usage. Modifying or disabling a network firewall may enable adversary C2 communications, lateral movement, and/or data exfiltration that would otherwise not be allowed. For example, adversaries may add new network firewall rules to allow access to all internal network subnets without restrictions.(Citation: Exposed Fortinet Fortigate firewall interface leads to LockBit Ransomware) Adversaries may gain access to the firewall management console via Valid Accounts or by exploiting a vulnerability. In some cases, threat actors may target firewalls that have been exposed to the internet Exploit Public-Facing Application.(Citation: CVE-2024-55591 Detail)

Adversaries may take control of preexisting sessions with remote services to move laterally in an environment. Users may use valid credentials to log into a service specifically designed to accept remote connections, such as telnet, SSH, and RDP. When a user logs into a service, a session will be established that will allow them to maintain a continuous interaction with that service. Adversaries may commandeer these sessions to carry out actions on remote systems. Remote Service Session Hijacking differs from use of Remote Services because it hijacks an existing session rather than creating a new session using Valid Accounts.(Citation: RDP Hijacking Medium)(Citation: Breach Post-mortem SSH Hijack)

Adversaries may hijack a legitimate user's SSH session to move laterally within an environment. Secure Shell (SSH) is a standard means of remote access on Linux and macOS systems. It allows a user to connect to another system via an encrypted tunnel, commonly authenticating through a password, certificate or the use of an asymmetric encryption key pair. In order to move laterally from a compromised host, adversaries may take advantage of trust relationships established with other systems via public key authentication in active SSH sessions by hijacking an existing connection to another system. This may occur through compromising the SSH agent itself or by having access to the agent's socket. If an adversary is able to obtain root access, then hijacking SSH sessions is likely trivial.(Citation: Slideshare Abusing SSH)(Citation: SSHjack Blackhat)(Citation: Clockwork SSH Agent Hijacking)(Citation: Breach Post-mortem SSH Hijack) SSH Hijacking differs from use of SSH because it hijacks an existing SSH session rather than creating a new session using Valid Accounts.

Adversaries may hijack a legitimate user’s remote desktop session to move laterally within an environment. Remote desktop is a common feature in operating systems. It allows a user to log into an interactive session with a system desktop graphical user interface on a remote system. Microsoft refers to its implementation of the Remote Desktop Protocol (RDP) as Remote Desktop Services (RDS).(Citation: TechNet Remote Desktop Services) Adversaries may perform RDP session hijacking which involves stealing a legitimate user's remote session. Typically, a user is notified when someone else is trying to steal their session. With System permissions and using Terminal Services Console, `c:\windows\system32\tscon.exe [session number to be stolen]`, an adversary can hijack a session without the need for credentials or prompts to the user.(Citation: RDP Hijacking Korznikov) This can be done remotely or locally and with active or disconnected sessions.(Citation: RDP Hijacking Medium) It can also lead to Remote System Discovery and Privilege Escalation by stealing a Domain Admin or higher privileged account session. All of this can be done by using native Windows commands, but it has also been added as a feature in red teaming tools.(Citation: Kali Redsnarf)

Adversaries may attempt to hide artifacts associated with their behaviors to evade detection. Operating systems may have features to hide various artifacts, such as important system files and administrative task execution, to avoid disrupting user work environments and prevent users from changing files or features on the system. Adversaries may abuse these features to hide artifacts such as files, directories, user accounts, or other system activity to evade detection.(Citation: Sofacy Komplex Trojan)(Citation: Cybereason OSX Pirrit)(Citation: MalwareBytes ADS July 2015) Adversaries may also attempt to hide artifacts associated with malicious behavior by creating computing regions that are isolated from common security instrumentation, such as through the use of virtualization technology.(Citation: Sophos Ragnar May 2020)

Adversaries may set files and directories to be hidden to evade detection mechanisms. To prevent normal users from accidentally changing special files on a system, most operating systems have the concept of a ‘hidden’ file. These files don’t show up when a user browses the file system with a GUI or when using normal commands on the command line. Users must explicitly ask to show the hidden files either via a series of Graphical User Interface (GUI) prompts or with command line switches (<code>dir /a</code> for Windows and <code>ls –a</code> for Linux and macOS). On Linux and Mac, users can mark specific files as hidden simply by putting a “.” as the first character in the file or folder name (Citation: Sofacy Komplex Trojan) (Citation: Antiquated Mac Malware). Files and folders that start with a period, ‘.’, are by default hidden from being viewed in the Finder application and standard command-line utilities like “ls”. Users must specifically change settings to have these files viewable. Files on macOS can also be marked with the UF_HIDDEN flag which prevents them from being seen in Finder.app, but still allows them to be seen in Terminal.app (Citation: WireLurker). On Windows, users can mark specific files as hidden by using the attrib.exe binary. Many applications create these hidden files and folders to store information so that it doesn’t clutter up the user’s workspace. For example, SSH utilities create a .ssh folder that’s hidden and contains the user’s known hosts and keys. Additionally, adversaries may name files in a manner that would allow the file to be hidden such as naming a file only a “space” character. Adversaries can use this to their advantage to hide files and folders anywhere on the system and evading a typical user or system analysis that does not incorporate investigation of hidden files.

Adversaries may use hidden users to hide the presence of user accounts they create or modify. Administrators may want to hide users when there are many user accounts on a given system or if they want to hide their administrative or other management accounts from other users. In macOS, adversaries can create or modify a user to be hidden through manipulating plist files, folder attributes, and user attributes. To prevent a user from being shown on the login screen and in System Preferences, adversaries can set the userID to be under 500 and set the key value <code>Hide500Users</code> to <code>TRUE</code> in the <code>/Library/Preferences/com.apple.loginwindow</code> plist file.(Citation: Cybereason OSX Pirrit) Every user has a userID associated with it. When the <code>Hide500Users</code> key value is set to <code>TRUE</code>, users with a userID under 500 do not appear on the login screen and in System Preferences. Using the command line, adversaries can use the <code>dscl</code> utility to create hidden user accounts by setting the <code>IsHidden</code> attribute to <code>1</code>. Adversaries can also hide a user’s home folder by changing the <code>chflags</code> to hidden.(Citation: Apple Support Hide a User Account) Adversaries may similarly hide user accounts in Windows. Adversaries can set the <code>HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList</code> Registry key value to <code>0</code> for a specific user to prevent that user from being listed on the logon screen.(Citation: FireEye SMOKEDHAM June 2021)(Citation: US-CERT TA18-074A) On Linux systems, adversaries may hide user accounts from the login screen, also referred to as the greeter. The method an adversary may use depends on which Display Manager the distribution is currently using. For example, on an Ubuntu system using the GNOME Display Manger (GDM), accounts may be hidden from the greeter using the <code>gsettings</code> command (ex: <code>sudo -u gdm gsettings set org.gnome.login-screen disable-user-list true</code>).(Citation: Hide GDM User Accounts) Display Managers are not anchored to specific distributions and may be changed by a user or adversary.

Adversaries may use hidden windows to conceal malicious activity from the plain sight of users. In some cases, windows that would typically be displayed when an application carries out an operation can be hidden. This may be utilized by system administrators to avoid disrupting user work environments when carrying out administrative tasks. Adversaries may abuse these functionalities to hide otherwise visible windows from users so as not to alert the user to adversary activity on the system.(Citation: Antiquated Mac Malware) On macOS, the configurations for how applications run are listed in property list (plist) files. One of the tags in these files can be <code>apple.awt.UIElement</code>, which allows for Java applications to prevent the application's icon from appearing in the Dock. A common use for this is when applications run in the system tray, but don't also want to show up in the Dock. Similarly, on Windows there are a variety of features in scripting languages, such as PowerShell, Jscript, and Visual Basic to make windows hidden. One example of this is <code>powershell.exe -WindowStyle Hidden</code>.(Citation: PowerShell About 2019) The Windows Registry can also be edited to hide application windows from the current user. For example, by setting the `WindowPosition` subkey in the `HKEY_CURRENT_USER\Console\%SystemRoot%_System32_WindowsPowerShell_v1.0_PowerShell.exe` Registry key to a maximum value, PowerShell windows will open off screen and be hidden.(Citation: Cantoris Computing) In addition, Windows supports the `CreateDesktop()` API that can create a hidden desktop window with its own corresponding <code>explorer.exe</code> process.(Citation: Hidden VNC)(Citation: Anatomy of an hVNC Attack) All applications running on the hidden desktop window, such as a hidden VNC (hVNC) session,(Citation: Hidden VNC) will be invisible to other desktops windows. Adversaries may also leverage cmd.exe(Citation: Cybereason - Hidden Malicious Remote Access) as a parent process, and then utilize a LOLBin, such as DeviceCredentialDeployment.exe,(Citation: LOLBAS Project GitHub Device Cred Dep)(Citation: SecureList BlueNoroff Device Cred Dev) to hide windows.

Adversaries may use NTFS file attributes to hide their malicious data in order to evade detection. Every New Technology File System (NTFS) formatted partition contains a Master File Table (MFT) that maintains a record for every file/directory on the partition. (Citation: SpectorOps Host-Based Jul 2017) Within MFT entries are file attributes, (Citation: Microsoft NTFS File Attributes Aug 2010) such as Extended Attributes (EA) and Data [known as Alternate Data Streams (ADSs) when more than one Data attribute is present], that can be used to store arbitrary data (and even complete files). (Citation: SpectorOps Host-Based Jul 2017) (Citation: Microsoft File Streams) (Citation: MalwareBytes ADS July 2015) (Citation: Microsoft ADS Mar 2014) Adversaries may store malicious data or binaries in file attribute metadata instead of directly in files. This may be done to evade some defenses, such as static indicator scanning tools and anti-virus. (Citation: Journey into IR ZeroAccess NTFS EA) (Citation: MalwareBytes ADS July 2015)

Adversaries may use a hidden file system to conceal malicious activity from users and security tools. File systems provide a structure to store and access data from physical storage. Typically, a user engages with a file system through applications that allow them to access files and directories, which are an abstraction from their physical location (ex: disk sector). Standard file systems include FAT, NTFS, ext4, and APFS. File systems can also contain other structures, such as the Volume Boot Record (VBR) and Master File Table (MFT) in NTFS.(Citation: MalwareTech VFS Nov 2014) Adversaries may use their own abstracted file system, separate from the standard file system present on the infected system. In doing so, adversaries can hide the presence of malicious components and file input/output from security tools. Hidden file systems, sometimes referred to as virtual file systems, can be implemented in numerous ways. One implementation would be to store a file system in reserved disk space unused by disk structures or standard file system partitions.(Citation: MalwareTech VFS Nov 2014)(Citation: FireEye Bootkits) Another implementation could be for an adversary to drop their own portable partition image as a file on top of the standard file system.(Citation: ESET ComRAT May 2020) Adversaries may also fragment files across the existing file system structure in non-standard ways.(Citation: Kaspersky Equation QA)

Adversaries may carry out malicious operations using a virtual instance to avoid detection. A wide variety of virtualization technologies exist that allow for the emulation of a computer or computing environment. By running malicious code inside of a virtual instance, adversaries can hide artifacts associated with their behavior from security tools that are unable to monitor activity inside the virtual instance.(Citation: CyberCX Akira Ransomware) Additionally, depending on the virtual networking implementation (ex: bridged adapter), network traffic generated by the virtual instance can be difficult to trace back to the compromised host as the IP address and hostname might not match known values.(Citation: SingHealth Breach Jan 2019) Adversaries may utilize native support for virtualization (ex: Hyper-V), deploy lightweight emulators (ex: QEMU), or drop the necessary files to run a virtual instance (ex: VirtualBox binaries).(Citation: Securonix CronTrap 2024) After running a virtual instance, adversaries may create a shared folder between the guest and host with permissions that enable the virtual instance to interact with the host file system.(Citation: Sophos Ragnar May 2020) Threat actors may also leverage temporary virtualized environments such as the Windows Sandbox, which supports the use of `.wsb` configuration files for defining execution parameters. For example, the `<MappedFolder>` property supports the creation of a shared folder, while the `<LogonCommand>` property allows the specification of a payload.(Citation: ESET MirrorFace 2025)(Citation: ITOCHU Hack the Sandbox)(Citation: ITOCHU Sandbox PPT) In VMWare environments, adversaries may leverage the vCenter console to create new virtual machines. However, they may also create virtual machines directly on ESXi servers by running a valid `.vmx` file with the `/bin/vmx` utility. Adding this command to `/etc/rc.local.d/local.sh` (i.e., RC Scripts) will cause the VM to persistently restart.(Citation: vNinja Rogue VMs 2024) Creating a VM this way prevents it from appearing in the vCenter console or in the output to the `vim-cmd vmsvc/getallvms` command on the ESXi server, thereby hiding it from typical administrative activities.(Citation: MITRE VMware Abuse 2024)

Adversaries may hide malicious Visual Basic for Applications (VBA) payloads embedded within MS Office documents by replacing the VBA source code with benign data.(Citation: FireEye VBA stomp Feb 2020) MS Office documents with embedded VBA content store source code inside of module streams. Each module stream has a <code>PerformanceCache</code> that stores a separate compiled version of the VBA source code known as p-code. The p-code is executed when the MS Office version specified in the <code>_VBA_PROJECT</code> stream (which contains the version-dependent description of the VBA project) matches the version of the host MS Office application.(Citation: Evil Clippy May 2019)(Citation: Microsoft _VBA_PROJECT Stream) An adversary may hide malicious VBA code by overwriting the VBA source code location with zero’s, benign code, or random bytes while leaving the previously compiled malicious p-code. Tools that scan for malicious VBA source code may be bypassed as the unwanted code is hidden in the compiled p-code. If the VBA source code is removed, some tools might even think that there are no macros present. If there is a version match between the <code>_VBA_PROJECT</code> stream and host MS Office application, the p-code will be executed, otherwise the benign VBA source code will be decompressed and recompiled to p-code, thus removing malicious p-code and potentially bypassing dynamic analysis.(Citation: Walmart Roberts Oct 2018)(Citation: FireEye VBA stomp Feb 2020)(Citation: pcodedmp Bontchev)

Adversaries may use email rules to hide inbound emails in a compromised user's mailbox. Many email clients allow users to create inbox rules for various email functions, including moving emails to other folders, marking emails as read, or deleting emails. Rules may be created or modified within email clients or through external features such as the <code>New-InboxRule</code> or <code>Set-InboxRule</code> PowerShell cmdlets on Windows systems.(Citation: Microsoft Inbox Rules)(Citation: MacOS Email Rules)(Citation: Microsoft New-InboxRule)(Citation: Microsoft Set-InboxRule) Adversaries may utilize email rules within a compromised user's mailbox to delete and/or move emails to less noticeable folders. Adversaries may do this to hide security alerts, C2 communication, or responses to Internal Spearphishing emails sent from the compromised account. Any user or administrator within the organization (or adversary with valid credentials) may be able to create rules to automatically move or delete emails. These rules can be abused to impair/delay detection had the email content been immediately seen by a user or defender. Malicious rules commonly filter out emails based on key words (such as <code>malware</code>, <code>suspicious</code>, <code>phish</code>, and <code>hack</code>) found in message bodies and subject lines. (Citation: Microsoft Cloud App Security) In some environments, administrators may be able to enable email rules that operate organization-wide rather than on individual inboxes. For example, Microsoft Exchange supports transport rules that evaluate all mail an organization receives against user-specified conditions, then performs a user-specified action on mail that adheres to those conditions.(Citation: Microsoft Mail Flow Rules 2023) Adversaries that abuse such features may be able to automatically modify or delete all emails related to specific topics (such as internal security incident notifications).

Adversaries may abuse resource forks to hide malicious code or executables to evade detection and bypass security applications. A resource fork provides applications a structured way to store resources such as thumbnail images, menu definitions, icons, dialog boxes, and code.(Citation: macOS Hierarchical File System Overview) Usage of a resource fork is identifiable when displaying a file’s extended attributes, using <code>ls -l@</code> or <code>xattr -l</code> commands. Resource forks have been deprecated and replaced with the application bundle structure. Non-localized resources are placed at the top level directory of an application bundle, while localized resources are placed in the <code>/Resources</code> folder.(Citation: Resource and Data Forks)(Citation: ELC Extended Attributes) Adversaries can use resource forks to hide malicious data that may otherwise be stored directly in files. Adversaries can execute content with an attached resource fork, at a specified offset, that is moved to an executable location then invoked. Resource fork content may also be obfuscated/encrypted until execution.(Citation: sentinellabs resource named fork 2020)(Citation: tau bundlore erika noerenberg 2020)

Adversaries may attempt to hide process command-line arguments by overwriting process memory. Process command-line arguments are stored in the process environment block (PEB), a data structure used by Windows to store various information about/used by a process. The PEB includes the process command-line arguments that are referenced when executing the process. When a process is created, defensive tools/sensors that monitor process creations may retrieve the process arguments from the PEB.(Citation: Microsoft PEB 2021)(Citation: Xpn Argue Like Cobalt 2019) Adversaries may manipulate a process PEB to evade defenses. For example, Process Hollowing can be abused to spawn a process in a suspended state with benign arguments. After the process is spawned and the PEB is initialized (and process information is potentially logged by tools/sensors), adversaries may override the PEB to modify the command-line arguments (ex: using the Native API <code>WriteProcessMemory()</code> function) then resume process execution with malicious arguments.(Citation: Cobalt Strike Arguments 2019)(Citation: Xpn Argue Like Cobalt 2019)(Citation: Nviso Spoof Command Line 2020) Adversaries may also execute a process with malicious command-line arguments then patch the memory with benign arguments that may bypass subsequent process memory analysis.(Citation: FireEye FiveHands April 2021) This behavior may also be combined with other tricks (such as Parent PID Spoofing) to manipulate or further evade process-based detections.

Adversaries may evade defensive mechanisms by executing commands that hide from process interrupt signals. Many operating systems use signals to deliver messages to control process behavior. Command interpreters often include specific commands/flags that ignore errors and other hangups, such as when the user of the active session logs off.(Citation: Linux Signal Man) These interrupt signals may also be used by defensive tools and/or analysts to pause or terminate specified running processes. Adversaries may invoke processes using `nohup`, PowerShell `-ErrorAction SilentlyContinue`, or similar commands that may be immune to hangups.(Citation: nohup Linux Man)(Citation: Microsoft PowerShell SilentlyContinue) This may enable malicious commands and malware to continue execution through system events that would otherwise terminate its execution, such as users logging off or the termination of its C2 network connection. Hiding from process interrupt signals may allow malware to continue execution, but unlike Trap this does not establish Persistence since the process will not be re-invoked once actually terminated.

Adversaries may attempt to hide their file-based artifacts by writing them to specific folders or file names excluded from antivirus (AV) scanning and other defensive capabilities. AV and other file-based scanners often include exclusions to optimize performance as well as ease installation and legitimate use of applications. These exclusions may be contextual (e.g., scans are only initiated in response to specific triggering events/alerts), but are also often hardcoded strings referencing specific folders and/or files assumed to be trusted and legitimate.(Citation: Microsoft File Folder Exclusions) Adversaries may abuse these exclusions to hide their file-based artifacts. For example, rather than tampering with tool settings to add a new exclusion (i.e., Disable or Modify Tools), adversaries may drop their file-based payloads in default or otherwise well-known exclusions. Adversaries may also use Security Software Discovery and other Discovery/Reconnaissance activities to both discover and verify existing exclusions in a victim environment.

Adversaries may abuse bind mounts on file structures to hide their activity and artifacts from native utilities. A bind mount maps a directory or file from one location on the filesystem to another, similar to a shortcut on Windows. It’s commonly used to provide access to specific files or directories across different environments, such as inside containers or chroot environments, and requires sudo access. Adversaries may use bind mounts to map either an empty directory or a benign `/proc` directory to a malicious process’s `/proc` directory. Using the commands `mount –o bind /proc/benign-process /proc/malicious-process` (or `mount –B`), the malicious process's `/proc` directory is overlayed with the contents of a benign process's `/proc` directory. When system utilities query process activity, such as `ps` and `top`, the kernel follows the bind mount and presents the benign directory’s contents instead of the malicious process's actual `/proc` directory. As a result, these utilities display information that appears to come from the benign process, effectively hiding the malicious process's metadata, executable, or other artifacts from detection.(Citation: Cado Security Commando Cat 2024)(Citation: Ahn Lab CoinMiner 2023)

Adversaries may abuse extended attributes (xattrs) on macOS and Linux to hide their malicious data in order to evade detection. Extended attributes are key-value pairs of file and directory metadata used by both macOS and Linux. They are not visible through standard tools like `Finder`, `ls`, or `cat` and require utilities such as `xattr` (macOS) or `getfattr` (Linux) for inspection. Operating systems and applications use xattrs for tagging, integrity checks, and access control. On Linux, xattrs are organized into namespaces such as `user.` (user permissions), `trusted.` (root permissions), `security.`, and `system.`, each with specific permissions. On macOS, xattrs are flat strings without namespace prefixes, commonly prefixed with `com.apple.*` (e.g., `com.apple.quarantine`, `com.apple.metadata:_kMDItemUserTags`) and used by system features like Gatekeeper and Spotlight.(Citation: Establishing persistence using extended attributes on Linux) An adversary may leverage xattrs by embedding a second-stage payload into the extended attribute of a legitimate file. On macOS, a payload can be embedded into a custom attribute using the `xattr` command. A separate loader can retrieve the attribute with `xattr -p`, decode the content, and execute it using a scripting interpreter. On Linux, an adversary may use `setfattr` to write a payload into the `user.` namespace of a legitimate file. A loader script can later extract the payload with `getfattr --only-values`, decode it, and execute it using bash or another interpreter. In both cases, because the primary file content remains unchanged, security tools and integrity checks that do not inspect extended attributes will observe the original file hash, allowing the malicious payload to evade detection.(Citation: Low GroupIB xattrs nov 2024)

Adversaries may insert, delete, or manipulate data in order to influence external outcomes or hide activity, thus threatening the integrity of the data.(Citation: Sygnia Elephant Beetle Jan 2022) By manipulating data, adversaries may attempt to affect a business process, organizational understanding, or decision making. The type of modification and the impact it will have depends on the target application and process as well as the goals and objectives of the adversary. For complex systems, an adversary would likely need special expertise and possibly access to specialized software related to the system that would typically be gained through a prolonged information gathering campaign in order to have the desired impact.

Adversaries may insert, delete, or manipulate data at rest in order to influence external outcomes or hide activity, thus threatening the integrity of the data.(Citation: FireEye APT38 Oct 2018)(Citation: DOJ Lazarus Sony 2018) By manipulating stored data, adversaries may attempt to affect a business process, organizational understanding, and decision making. Stored data could include a variety of file formats, such as Office files, databases, stored emails, and custom file formats. The type of modification and the impact it will have depends on the type of data as well as the goals and objectives of the adversary. For complex systems, an adversary would likely need special expertise and possibly access to specialized software related to the system that would typically be gained through a prolonged information gathering campaign in order to have the desired impact.

Adversaries may alter data en route to storage or other systems in order to manipulate external outcomes or hide activity, thus threatening the integrity of the data.(Citation: FireEye APT38 Oct 2018)(Citation: DOJ Lazarus Sony 2018) By manipulating transmitted data, adversaries may attempt to affect a business process, organizational understanding, and decision making. Manipulation may be possible over a network connection or between system processes where there is an opportunity deploy a tool that will intercept and change information. The type of modification and the impact it will have depends on the target transmission mechanism as well as the goals and objectives of the adversary. For complex systems, an adversary would likely need special expertise and possibly access to specialized software related to the system that would typically be gained through a prolonged information gathering campaign in order to have the desired impact.

Adversaries may modify systems in order to manipulate the data as it is accessed and displayed to an end user, thus threatening the integrity of the data.(Citation: FireEye APT38 Oct 2018)(Citation: DOJ Lazarus Sony 2018) By manipulating runtime data, adversaries may attempt to affect a business process, organizational understanding, and decision making. Adversaries may alter application binaries used to display data in order to cause runtime manipulations. Adversaries may also conduct Change Default File Association and Masquerading to cause a similar effect. The type of modification and the impact it will have depends on the target application and process as well as the goals and objectives of the adversary. For complex systems, an adversary would likely need special expertise and possibly access to specialized software related to the system that would typically be gained through a prolonged information gathering campaign in order to have the desired impact.

Adversaries may send phishing messages to gain access to victim systems. All forms of phishing are electronically delivered social engineering. Phishing can be targeted, known as spearphishing. In spearphishing, a specific individual, company, or industry will be targeted by the adversary. More generally, adversaries can conduct non-targeted phishing, such as in mass malware spam campaigns. Adversaries may send victims emails containing malicious attachments or links, typically to execute malicious code on victim systems. Phishing may also be conducted via third-party services, like social media platforms. Phishing may also involve social engineering techniques, such as posing as a trusted source, as well as evasive techniques such as removing or manipulating emails or metadata/headers from compromised accounts being abused to send messages (e.g., Email Hiding Rules).(Citation: Microsoft OAuth Spam 2022)(Citation: Palo Alto Unit 42 VBA Infostealer 2014) Another way to accomplish this is by Email Spoofing(Citation: Proofpoint-spoof) the identity of the sender, which can be used to fool both the human recipient as well as automated security tools,(Citation: cyberproof-double-bounce) or by including the intended target as a party to an existing email thread that includes malicious files or links (i.e., "thread hijacking").(Citation: phishing-krebs) Victims may also receive phishing messages that instruct them to call a phone number where they are directed to visit a malicious URL, download malware,(Citation: sygnia Luna Month)(Citation: CISA Remote Monitoring and Management Software) or install adversary-accessible remote management tools onto their computer (i.e., User Execution).(Citation: Unit42 Luna Moth)

Adversaries may send spearphishing emails with a malicious attachment in an attempt to gain access to victim systems. Spearphishing attachment is a specific variant of spearphishing. Spearphishing attachment is different from other forms of spearphishing in that it employs the use of malware attached to an email. All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this scenario, adversaries attach a file to the spearphishing email and usually rely upon User Execution to gain execution.(Citation: Unit 42 DarkHydrus July 2018) Spearphishing may also involve social engineering techniques, such as posing as a trusted source. There are many options for the attachment such as Microsoft Office documents, executables, PDFs, or archived files. Upon opening the attachment (and potentially clicking past protections), the adversary's payload exploits a vulnerability or directly executes on the user's system. The text of the spearphishing email usually tries to give a plausible reason why the file should be opened, and may explain how to bypass system protections in order to do so. The email may also contain instructions on how to decrypt an attachment, such as a zip file password, in order to evade email boundary defenses. Adversaries frequently manipulate file extensions and icons in order to make attached executables appear to be document files, or files exploiting one application appear to be a file for a different one.

Adversaries may send spearphishing emails with a malicious link in an attempt to gain access to victim systems. Spearphishing with a link is a specific variant of spearphishing. It is different from other forms of spearphishing in that it employs the use of links to download malware contained in email, instead of attaching malicious files to the email itself, to avoid defenses that may inspect email attachments. Spearphishing may also involve social engineering techniques, such as posing as a trusted source. All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this case, the malicious emails contain links. Generally, the links will be accompanied by social engineering text and require the user to actively click or copy and paste a URL into a browser, leveraging User Execution. The visited website may compromise the web browser using an exploit, or the user will be prompted to download applications, documents, zip files, or even executables depending on the pretext for the email in the first place. Adversaries may also include links that are intended to interact directly with an email reader, including embedded images intended to exploit the end system directly. Additionally, adversaries may use seemingly benign links that abuse special characters to mimic legitimate websites (known as an "IDN homograph attack").(Citation: CISA IDN ST05-016) URLs may also be obfuscated by taking advantage of quirks in the URL schema, such as the acceptance of integer- or hexadecimal-based hostname formats and the automatic discarding of text before an “@” symbol: for example, `hxxp://google.com@1157586937`.(Citation: Mandiant URL Obfuscation 2023) Adversaries may also utilize links to perform consent phishing/spearphishing campaigns to Steal Application Access Tokens that grant immediate access to the victim environment. For example, a user may be lured into granting adversaries permissions/access via a malicious OAuth 2.0 request URL that when accepted by the user provide permissions/access for malicious applications.(Citation: Trend Micro Pawn Storm OAuth 2017)(Citation: Microsoft OAuth 2.0 Consent Phishing 2021) These stolen access tokens allow the adversary to perform various actions on behalf of the user via API calls.(Citation: Microsoft OAuth 2.0 Consent Phishing 2021) Similarly, malicious links may also target device-based authorization, such as OAuth 2.0 device authorization grant flow which is typically used to authenticate devices without UIs/browsers. Known as “device code phishing,” an adversary may send a link that directs the victim to a malicious authorization page where the user is tricked into entering a code/credentials that produces a device token.(Citation: SecureWorks Device Code Phishing 2021)(Citation: Netskope Device Code Phishing 2021)(Citation: Optiv Device Code Phishing 2021)

Adversaries may send spearphishing messages via third-party services in an attempt to gain access to victim systems. Spearphishing via service is a specific variant of spearphishing. It is different from other forms of spearphishing in that it employs the use of third party services rather than directly via enterprise email channels. All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this scenario, adversaries send messages through various social media services, personal webmail, and other non-enterprise controlled services.(Citation: Lookout Dark Caracal Jan 2018) These services are more likely to have a less-strict security policy than an enterprise. As with most kinds of spearphishing, the goal is to generate rapport with the target or get the target's interest in some way. Adversaries will create fake social media accounts and message employees for potential job opportunities. Doing so allows a plausible reason for asking about services, policies, and software that's running in an environment. The adversary can then send malicious links or attachments through these services. A common example is to build rapport with a target via social media, then send content to a personal webmail service that the target uses on their work computer. This allows an adversary to bypass some email restrictions on the work account, and the target is more likely to open the file since it's something they were expecting. If the payload doesn't work as expected, the adversary can continue normal communications and troubleshoot with the target on how to get it working.

Adversaries may use voice communications to ultimately gain access to victim systems. Spearphishing voice is a specific variant of spearphishing. It is different from other forms of spearphishing in that it employs the use of manipulating a user into providing access to systems through a phone call or other forms of voice communications. Spearphishing frequently involves social engineering techniques, such as posing as a trusted source (ex: Impersonation) and/or creating a sense of urgency or alarm for the recipient. All forms of phishing are electronically delivered social engineering. In this scenario, adversaries are not directly sending malware to a victim vice relying on User Execution for delivery and execution. For example, victims may receive phishing messages that instruct them to call a phone number where they are directed to visit a malicious URL, download malware,(Citation: sygnia Luna Month)(Citation: CISA Remote Monitoring and Management Software) or install adversary-accessible remote management tools (Remote Access Tools) onto their computer.(Citation: Unit42 Luna Moth) Adversaries may also combine voice phishing with Multi-Factor Authentication Request Generation in order to trick users into divulging MFA credentials or accepting authentication prompts.(Citation: Proofpoint Vishing)

Adversaries may use an existing, legitimate external Web service to exfiltrate data rather than their primary command and control channel. Popular Web services acting as an exfiltration mechanism may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to compromise. Firewall rules may also already exist to permit traffic to these services. Web service providers also commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Adversaries may exfiltrate data to a code repository rather than over their primary command and control channel. Code repositories are often accessible via an API (ex: https://api.github.com). Access to these APIs are often over HTTPS, which gives the adversary an additional level of protection. Exfiltration to a code repository can also provide a significant amount of cover to the adversary if it is a popular service already used by hosts within the network.

Adversaries may exfiltrate data to a cloud storage service rather than over their primary command and control channel. Cloud storage services allow for the storage, edit, and retrieval of data from a remote cloud storage server over the Internet. Examples of cloud storage services include Dropbox and Google Docs. Exfiltration to these cloud storage services can provide a significant amount of cover to the adversary if hosts within the network are already communicating with the service.

Adversaries may exfiltrate data to text storage sites instead of their primary command and control channel. Text storage sites, such as <code>pastebin[.]com</code>, are commonly used by developers to share code and other information. Text storage sites are often used to host malicious code for C2 communication (e.g., Stage Capabilities), but adversaries may also use these sites to exfiltrate collected data. Furthermore, paid features and encryption options may allow adversaries to conceal and store data more securely.(Citation: Pastebin EchoSec) **Note:** This is distinct from Exfiltration to Code Repository, which highlight access to code repositories via APIs.

Adversaries may exfiltrate data to a webhook endpoint rather than over their primary command and control channel. Webhooks are simple mechanisms for allowing a server to push data over HTTP/S to a client without the need for the client to continuously poll the server.(Citation: RedHat Webhooks) Many public and commercial services, such as Discord, Slack, and `webhook.site`, support the creation of webhook endpoints that can be used by other services, such as Github, Jira, or Trello.(Citation: Discord Intro to Webhooks) When changes happen in the linked services (such as pushing a repository update or modifying a ticket), these services will automatically post the data to the webhook endpoint for use by the consuming application. Adversaries may link an adversary-owned environment to a victim-owned SaaS service to achieve repeated Automated Exfiltration of emails, chat messages, and other data.(Citation: Push Security SaaS Attacks Repository Webhooks) Alternatively, instead of linking the webhook endpoint to a service, an adversary can manually post staged data directly to the URL in order to exfiltrate it.(Citation: Microsoft SQL Server) Access to webhook endpoints is often over HTTPS, which gives the adversary an additional level of protection. Exfiltration leveraging webhooks can also blend in with normal network traffic if the webhook endpoint points to a commonly used SaaS application or collaboration service.(Citation: CyberArk Labs Discord)(Citation: Talos Discord Webhook Abuse)(Citation: Checkmarx Webhooks)

Adversaries may dynamically establish connections to command and control infrastructure to evade common detections and remediations. This may be achieved by using malware that shares a common algorithm with the infrastructure the adversary uses to receive the malware's communications. These calculations can be used to dynamically adjust parameters such as the domain name, IP address, or port number the malware uses for command and control. Adversaries may use dynamic resolution for the purpose of Fallback Channels. When contact is lost with the primary command and control server malware may employ dynamic resolution as a means to reestablishing command and control.(Citation: Talos CCleanup 2017)(Citation: FireEye POSHSPY April 2017)(Citation: ESET Sednit 2017 Activity)

Adversaries may use Fast Flux DNS to hide a command and control channel behind an array of rapidly changing IP addresses linked to a single domain resolution. This technique uses a fully qualified domain name, with multiple IP addresses assigned to it which are swapped with high frequency, using a combination of round robin IP addressing and short Time-To-Live (TTL) for a DNS resource record.(Citation: MehtaFastFluxPt1)(Citation: MehtaFastFluxPt2)(Citation: Fast Flux - Welivesecurity) The simplest, "single-flux" method, involves registering and de-registering an addresses as part of the DNS A (address) record list for a single DNS name. These registrations have a five-minute average lifespan, resulting in a constant shuffle of IP address resolution.(Citation: Fast Flux - Welivesecurity) In contrast, the "double-flux" method registers and de-registers an address as part of the DNS Name Server record list for the DNS zone, providing additional resilience for the connection. With double-flux additional hosts can act as a proxy to the C2 host, further insulating the true source of the C2 channel.