Detection: Windows Rundll32 Inline HTA Execution

Description

The following analytic identifies "rundll32.exe" execution with inline protocol handlers. "JavaScript", "VBScript", and "About" are the only supported options when invoking HTA content directly on the command-line. This type of behavior is commonly observed with fileless malware or application whitelisting bypass techniques. The search will return the first time and last time these command-line arguments were used for these executions, as well as the target system, the user, process "rundll32.exe" and its parent process.

Annotations

No annotations available.

Implementation

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

Although unlikely, some legitimate applications may exhibit this behavior, triggering a false positive.

Associated Analytic Story

• Suspicious MSHTA Activity

• NOBELIUM Group

• Living Off The Land

Risk Based Analytics (RBA)

References

• https://github.com/redcanaryco/AtomicTestHarnesses

• https://redcanary.com/blog/introducing-atomictestharnesses/

• https://docs.microsoft.com/en-us/windows/win32/search/-search-3x-wds-extidx-prot-implementing

Version: 4