Indirect Command Execution

What the technique is

Adversaries may abuse utilities that allow for command execution to bypass security restrictions that limit the use of command-line interpreters. Various Windows utilities may be used to execute commands, possibly without invoking cmd. For example, Forfiles, the Program Compatibility Assistant (pcalua.exe), components of the Windows Subsystem for Linux (WSL), Scriptrunner.exe, as well as other utilities may invoke the execution of programs and commands from a Command and Scripting Interpreter, Run window, or via scripts. Adversaries may also abuse the ssh.exe binary to execute malicious commands via the ProxyCommand and LocalCommand options, which can be invoked via the -o flag or by modifying the SSH config file. Adversaries may abuse these features for Stealth, specifically to perform arbitrary execution while subverting detections and/or mitigation controls (such as Group Policy) that limit/prevent the usage of cmd or file extensions more commonly associated with malicious payloads.

What MITRE says you would watch

• AN0576

  Cause→effect chain: (1) A user or service launches an indirection utility (e.g., forfiles.exe, pcalua.exe, wsl.exe, scriptrunner.exe, ssh.exe with -o ProxyCommand/LocalCommand). (2) That utility spawns a secondary program/command (PowerShell, cmd, msiexec, regsvr32, curl, arbitrary EXE) and/or opens outbound network connections. (3) Optional precursor modification of SSH config to persist LocalCommand/ProxyCommand. Correlate process creation, command/script content, file access to %USERPROFILE%\.ssh\config, and network connections from the utility or its child.