Taint Shared Content

What the technique is

Adversaries may deliver payloads to remote systems by adding content to shared storage locations, such as network drives or internal code repositories. Content stored on network drives or in other shared locations may be tainted by adding malicious programs, scripts, or exploit code to otherwise valid files. Once a user opens the shared tainted content, the malicious portion can be executed to run the adversary's code on a remote system. Adversaries may use tainted shared content to move laterally. A directory share pivot is a variation on this technique that uses several other techniques to propagate malware when users access a shared network directory. It uses Shortcut Modification of directory.LNK files that use Masquerading to look like the real directories, which are hidden through Hidden Files and Directories. The malicious.LNK-based directories have an embedded command that executes the hidden malware file in the directory and then opens the real intended directory so that the user's expected action still occurs. When used with frequently used network directories, the technique may result in frequent reinfections and broad access to systems and potentially to new and higher privileged accounts. Adversaries may also compromise shared network directories through binary infections by appending or prepending its code to the healthy binary on the shared network directory. […]

What MITRE says you would watch

• AN1298

  Detects adversary tampering of shared directories via file drops (e.g., malicious LNK, EXE, VBS) followed by user execution or suspicious network activity.

• AN1299

  Detects script or binary modification within shared NFS/SMB directories followed by process execution from those paths.

• AN1300

  Detects modification of shared network folders via.app bundles or scripting files with hidden extensions (e.g., double extensions like docx.app).