Compromise Host Software Binary

What the technique is

Adversaries may modify host software binaries to establish persistent access to systems. Software binaries/executables provide a wide range of system commands or services, programs, and libraries. Common software binaries are SSH clients, FTP clients, email clients, web browsers, and many other user or server applications. Adversaries may establish persistence though modifications to host software binaries. For example, an adversary may replace or otherwise infect a legitimate application binary (or support files) with a backdoor. Since these binaries may be routinely executed by applications or the user, the adversary can leverage this for persistent access to the host. An adversary may also modify a software binary such as an SSH client in order to persistently collect credentials during logins (i.e., Modify Authentication Process). An adversary may also modify an existing binary by patching in malicious functionality (e.g., IAT Hooking/Entry point patching) prior to the binary’s legitimate execution. For example, an adversary may modify the entry point of a binary to point to malicious code patched in by the adversary before resuming normal execution flow. After modifying a binary, an adversary may attempt to impair defenses by preventing it from updating (e.g., via the yum-versionlock command or versionlock.list file in Linux systems that use the yum package manager).

What MITRE says you would watch

• AN0949

  Monitors for unexpected modifications of system or application binaries, particularly signed executables. Correlates file write events with subsequent unsigned or anomalously signed process execution, and checks for tampered binaries outside normal patch cycles.

• AN0950

  Detects modification of system or application binaries by monitoring /usr/bin, /bin, and other privileged directories. Correlates file integrity monitoring (FIM) events with unexpected process executions or service restarts.

• AN0951

  Monitors binary modification in /Applications and system library paths. Detects unsigned or improperly signed binaries executed after modification. Tracks Gatekeeper or notarization bypass attempts tied to modified binaries.