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Description

The following analytic identifies new printer drivers being load by utilizing the Windows PrintService operational logs, EventCode 316. This was identified during our testing of CVE-2021-34527 previously (CVE-2021-1675) or PrintNightmare.
Within the proof of concept code, the following event will occur - "Printer driver 1234 for Windows x64 Version-3 was added or updated. Files:- UNIDRV.DLL, kernelbase.dll, evil.dll. No user action is required."
During triage, isolate the endpoint and review for source of exploitation. Capture any additional file modification events and review the source of where the exploitation began.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-07-01
  • Author: Mauricio Velazco, Michael Haag, Teoderick Contreras, Splunk
  • ID: 313681a2-da8e-11eb-adad-acde48001122

ATT&CK

ID Technique Tactic
T1547.012 Print Processors Persistence, Privilege Escalation
T1547 Boot or Logon Autostart Execution Persistence, Privilege Escalation
`printservice` EventCode=316 category = "Adding a printer driver" Message = "*kernelbase.dll,*" Message = "*UNIDRV.DLL,*" Message = "*.DLL.*" 
| stats  count min(_time) as firstTime max(_time) as lastTime by OpCode EventCode ComputerName Message 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `print_spooler_adding_a_printer_driver_filter`

Associated Analytic Story

How To Implement

You will need to ensure PrintService Admin and Operational logs are being logged to Splunk from critical or all systems.

Required field

  • _time
  • OpCode
  • EventCode
  • ComputerName
  • Message

Kill Chain Phase

  • Exploitation

Known False Positives

Unknown. This may require filtering.

RBA

Risk Score Impact Confidence Message
72.0 80 90 Suspicious print driver was loaded on endpoint $ComputerName$.

CVE

ID Summary CVSS
CVE-2021-34527 Windows Print Spooler Remote Code Execution Vulnerability 9.0
CVE-2021-1675 Windows Print Spooler Elevation of Privilege Vulnerability 9.3

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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