Print Spooler Adding A Printer Driver
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
Kill Chain Phase
|CVE-2021-34527||Windows Print Spooler Remote Code Execution Vulnerability||9.0|
|CVE-2021-1675||Windows Print Spooler Elevation of Privilege Vulnerability||9.3|
1 2 3 4 5 `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`
The SPL above uses the following Macros:
print_spooler_adding_a_printer_driver_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
You will need to ensure PrintService Admin and Operational logs are being logged to Splunk from critical or all systems.
Known False Positives
Unknown. This may require filtering.
Associated Analytic Story
|72.0||80||90||Suspicious print driver was loaded on endpoint $ComputerName$.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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