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MediumSplunk security contentMauricio Velazco +1

Spoolsv Writing a DLL - Sysmon

The following analytic detects `spoolsv.exe` writing a `.dll` file, which is unusual behavior and may indicate exploitation of vulnerabilities like CVE-2021-34527 (PrintNightmare). This detection leverages Sysmon…

Description

The following analytic detects `spoolsv.exe` writing a `.dll` file, which is unusual behavior and may indicate exploitation of vulnerabilities like CVE-2021-34527 (PrintNightmare). This detection leverages Sysmon EventID 11 to monitor file creation events in the `\spool\drivers\x64\` directory. This activity is significant because `spoolsv.exe` typically does not write DLL files, and such behavior could signify an ongoing attack. If confirmed malicious, this could allow an attacker to execute arbitrary code, escalate privileges, or maintain persistence on the compromised system.

Detection logic

Detection requirements

Platform
Windows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
sysmon_eventid_11

Known benign triggers

  • Limited false positives. Filter as needed.

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