T1100

A Web shell is a Web script that is placed on an openly accessible Web server to allow an adversary to use the Web server as a gateway into a network. A Web shell may provide a set of functions to execute or a command-line interface on the system that hosts the Web server. In addition to a server-side script, a Web shell may have a client interface program that is used to talk to the Web server (see, for example, China Chopper Web shell client). (Citation: Lee 2013) Web shells may serve as [Redundant Access](https://attack.mitre.org/techniques/T1108) or as a persistence mechanism in case an adversary's primary access methods are detected and removed.