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.¹ 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 <code>AddPrintProcessor</code> API call with an account that has <code>SeLoadDriverPrivilege</code> enabled. Alternatively, a print processor can be registered to the print spooler service by adding the <code>HKLM\SYSTEM\\[CurrentControlSet or ControlSet001]\Control\Print\Environments\\[Windows architecture: e.g., Windows x64]\Print Processors\\[user defined]\Driver</code> 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 <code>GetPrintProcessorDirectory</code> API call, or referenced via a relative path from this directory.² 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.

1. Microsoft Intro Print Processors
2. Microsoft AddPrintProcessor May 2018
3. ESET PipeMon May 2020

使用该技术的组织

断言

尚无指向该技术的公开断言。

记录自动入库·未人工复核；置信度与有效期按引用读取。