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T1547.012 Print Processors

Adversaries may abuse print processors to run malicious DLLs during system boot for persistence and/or privilege escalation. Print processors are DLLs that are loaded by the print spooler service, spoolsv.exe, during boot.2

Adversaries may abuse the print spooler service by adding print processors that load malicious DLLs at startup. A print processor can be installed through the AddPrintProcessor API call with an account that has SeLoadDriverPrivilege enabled. Alternatively, a print processor can be registered to the print spooler service by adding the HKLM\SYSTEM\[CurrentControlSet or ControlSet001]\Control\Print\Environments\[Windows architecture: e.g., Windows x64]\Print Processors\[user defined]\Driver Registry key that points to the DLL.

For the malicious print processor to be correctly installed, the payload must be located in the dedicated system print-processor directory, that can be found with the GetPrintProcessorDirectory API call, or referenced via a relative path from this directory.1 After the print processors are installed, the print spooler service, which starts during boot, must be restarted in order for them to run.3

The print spooler service runs under SYSTEM level permissions, therefore print processors installed by an adversary may run under elevated privileges.

Item Value
ID T1547.012
Sub-techniques T1547.001, T1547.002, T1547.003, T1547.004, T1547.005, T1547.006, T1547.007, T1547.008, T1547.009, T1547.010, T1547.012, T1547.013, T1547.014, T1547.015
Tactics TA0003, TA0004
Platforms Windows
Version 1.2
Created 05 October 2020
Last Modified 24 October 2025

Procedure Examples

ID Name Description
G1006 Earth Lusca Earth Lusca has added the Registry key HKLM\SYSTEM\ControlSet001\Control\Print\Environments\Windows x64\Print Processors\UDPrint” /v Driver /d “spool.dll /f to load malware as a Print Processor.5
S0666 Gelsemium Gelsemium can drop itself in C:\Windows\System32\spool\prtprocs\x64\winprint.dll to be loaded automatically by the spoolsv Windows service.4
S0501 PipeMon The PipeMon installer has modified the Registry key HKLM\SYSTEM\CurrentControlSet\Control\Print\Environments\Windows x64\Print Processors to install PipeMon as a Print Processor.3

Mitigations

ID Mitigation Description
M1018 User Account Management Limit user accounts that can load or unload device drivers by disabling SeLoadDriverPrivilege.

References

  1. Microsoft. (2018, May 31). AddPrintProcessor function. Retrieved October 5, 2020. ↩

  2. Microsoft. (2023, June 26). Introduction to print processors. Retrieved September 27, 2023. ↩

  3. Tartare, M. et al. (2020, May 21). No “Game over” for the Winnti Group. Retrieved August 24, 2020. ↩↩

  4. Dupuy, T. and Faou, M. (2021, June). Gelsemium. Retrieved November 30, 2021. ↩

  5. Chen, J., et al. (2022). Delving Deep: An Analysis of Earth Lusca’s Operations. Retrieved July 1, 2022. ↩