Unusual Print Spooler Child Process

Elastic Stack Serverless Security

Detects unusual Print Spooler service (spoolsv.exe) child processes. This may indicate an attempt to exploit privilege escalation vulnerabilities related to the Printing Service on Windows.

Rule type: eql

Rule indices:

• winlogbeat-*
• logs-endpoint.events.*
• logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Privilege Escalation

Version: 101

Rule authors:

• Elastic

Rule license: Elastic License v2

process where event.type == "start" and
 process.parent.name : "spoolsv.exe" and
 (?process.Ext.token.integrity_level_name : "System" or
 ?winlog.event_data.IntegrityLevel : "System") and

 /* exclusions for FP control below */
 not process.name : ("splwow64.exe", "PDFCreator.exe", "acrodist.exe", "spoolsv.exe", "msiexec.exe", "route.exe", "WerFault.exe") and
 not process.command_line : "*\\WINDOWS\\system32\\spool\\DRIVERS*" and
 not (process.name : "net.exe" and process.command_line : ("*stop*", "*start*")) and
 not (process.name : ("cmd.exe", "powershell.exe") and process.command_line : ("*.spl*", "*\\program files*", "*route add*")) and
 not (process.name : "netsh.exe" and process.command_line : ("*add portopening*", "*rule name*")) and
 not (process.name : "regsvr32.exe" and process.command_line : "*PrintConfig.dll*")

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Privilege Escalation
  • ID: TA0004
  • Reference URL: https://attack.mitre.org/tactics/TA0004/

• Technique:

  • Name: Exploitation for Privilege Escalation
  • ID: T1068
  • Reference URL: https://attack.mitre.org/techniques/T1068/