ImageLoad via Windows Update Auto Update Client

Identifies abuse of the Windows Update Auto Update Client (wuauclt.exe) to load an arbitrary DLL. This behavior is used as a defense evasion technique to blend-in malicious activity with legitimate Windows software.

Rule type: eql

Rule indices:

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Version: 7 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 8.3.0

Rule authors: Elastic

Rule license: Elastic License v2

## Config

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

process where event.type in ("start", "process_started") and
(process.pe.original_file_name == "wuauclt.exe" or process.name :
"wuauclt.exe") and /* necessary windows update client args to load
a dll */ process.args : "/RunHandlerComServer" and process.args :
"/UpdateDeploymentProvider" and /* common paths writeable by a
standard user where the target DLL can be placed */ process.args :
("C:\\Users\\*.dll", "C:\\ProgramData\\*.dll",
"C:\\Windows\\Temp\\*.dll", "C:\\Windows\\Tasks\\*.dll")