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Splunk Lantern

Print spooler failing to load a plug-in

Some attacks such as PrintNightmare cause driver load errors utilizing the Windows PrintService Admin logs. This search detects instances of this taking place.

Data required 

Windows event logs

Procedure

  1. Ensure PrintService Admin and Operational logs are being logged to Splunk from critical or all systems.
  2. Run the following search. You can optimize it by specifying an index and adjusting the time range.
source="WinEventLog:Microsoft-Windows-PrintService/Admin" 
((ErrorCode="0x45A" (EventCode="808" OR EventCode="4909")) OR ("The print spooler failed to load a plug-in module" OR "\\drivers\\x64\\")) 
| stats count min(_time) AS firstTime max(_time) AS lastTime BY OpCode EventCode ComputerName Message

Search explanation

The table provides an explanation of what each part of this search achieves. You can adjust this query based on the specifics of your environment.

Splunk Search Explanation
source="WinEventLog:Microsoft-Windows-PrintService/Admin"  Search Windows PrintService administrative data.
((ErrorCode="0x45A" (EventCode="808" OR EventCode="4909")) OR ("The print spooler failed to load a plug-in module" OR "\\drivers\\x64\\")) Search for events with ErrorCode AND one of two possible EventCodes, and if not found look for events with one OR both of two possible strings as shown.
| stats count min(_time) AS firstTime max(_time) AS lastTime BY OpCode EventCode ComputerName Message Returns values for the first and last times these errors occurred, sorting first by operational code, and then by the rest of the fields shown.

Next steps

Ensure you filter for false positives on this search. 

During triage, isolate the endpoint and review for source of exploitation. Capture any additional file modification events.

If your results indicate an attack has occurred, the host or computer where the vulnerability is detected needs to be further investigated and remediated according to your response plan. This involves a final step of re-imaging the system with a known good system build after investigation.

Finally, you might be interested in other processes associated with the Detecting print spooler attacks use case.