LoFP / it is possible some administrative utilities will load msi.dll outside of normal system paths, filter as needed.

Techniques

• T1574
• T1574.002

Sample rules

MSI Module Loaded by Non-System Binary

• source: splunk
• technicques:
  • T1574.002
  • T1574

Description

The following hunting analytic identifies msi.dll being loaded by a binary not located in system32, syswow64, winsxs or windows paths. This behavior is most recently related to InstallerFileTakeOver, or CVE-2021-41379, and DLL side-loading. CVE-2021-41379 requires a binary to be dropped and msi.dll to be loaded by it. To Successful exploitation of this issue happens in four parts

1. Generation of an MSI that will trigger bad behavior.
2. Preparing a directory for MSI installation.
3. Inducing an error state.
4. Racing to introduce a junction and a symlink to trick msiexec.exe to modify the attacker specified file. In addition, msi.dll has been abused in DLL side-loading attacks by being loaded by non-system binaries.

Detection logic

`sysmon` EventCode=7 ImageLoaded="*\\msi.dll" NOT (Image IN ("*\\System32\\*","*\\syswow64\\*","*\\windows\\*", "*\\winsxs\\*")) 
| stats count min(_time) as firstTime max(_time) as lastTime by Image ImageLoaded process_name dest EventCode ProcessId 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `msi_module_loaded_by_non_system_binary_filter`