Unusual Print Spooler Child Process

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 (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: 6

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

edit

## Config

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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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&CK^TM

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/

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