splunk-security_content/docs/_posts/2021-07-01-spoolsv_suspicious_process_access.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Spoolsv Suspicious Process Access	Exploitation for Privilege Escalation	Endpoint	2021-07-01	true		Exploitation for Privilege Escalation Privilege Escalation Splunk Enterprise Splunk Enterprise Security Splunk Cloud CVE-2021-34527 Endpoint

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Description

This analytic identifies a suspicious behavior related to PrintNightmare, or CVE-2021-34527 previously (CVE-2021-1675), to gain privilege escalation on the vulnerable machine. This exploit attacks a critical Windows Print Spooler Vulnerability to elevate privilege. This detection is to look for suspicious process access made by the spoolsv.exe that may related to the attack.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-07-01
• Author: Mauricio Velazco, Michael Haag, Teoderick Contreras, Splunk
• ID: 799b606e-da81-11eb-93f8-acde48001122

ATT&CK

ID	Technique	Tactic
T1068	Exploitation for Privilege Escalation	Privilege Escalation

Search

`sysmon` EventCode=10 SourceImage = "*\\spoolsv.exe" CallTrace = "*\\Windows\\system32\\spool\\DRIVERS\\x64\\*" TargetImage IN ("*\\rundll32.exe", "*\\spoolsv.exe") GrantedAccess = 0x1fffff 
| stats  count min(_time) as firstTime max(_time) as lastTime by Computer SourceImage TargetImage GrantedAccess CallTrace  EventCode ProcessID
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `spoolsv_suspicious_process_access_filter`

Associated Analytic Story

• PrintNightmare CVE-2021-34527

How To Implement

To successfully implement this search, you need to be ingesting logs with process access event where SourceImage, TargetImage, GrantedAccess and CallTrace executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances of spoolsv.exe.

Required field

• _time
• SourceImage
• TargetImage
• GrantedAccess
• CallTrace
• EventCode

Kill Chain Phase

• Exploitation

Known False Positives

Unknown. Filter as needed.

RBA

Risk Score	Impact	Confidence	Message
72.0	80	90	SourceImage was GrantedAccess open access to TargetImage on endpoint Computer. This behavior is suspicious and related to PrintNightmare.

CVE

ID	Summary	CVSS
CVE-2021-34527	Windows Print Spooler Remote Code Execution Vulnerability	9.0

Reference

• https://github.com/cube0x0/impacket/commit/73b9466c17761384ece11e1028ec6689abad6818
• https://blog.truesec.com/2021/06/30/fix-for-printnightmare-cve-2021-1675-exploit-to-keep-your-print-servers-running-while-a-patch-is-not-available/
• https://blog.truesec.com/2021/06/30/exploitable-critical-rce-vulnerability-allows-regular-users-to-fully-compromise-active-directory-printnightmare-cve-2021-1675/
• https://www.reddit.com/r/msp/comments/ob6y02/critical_vulnerability_printnightmare_exposes

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1547.012/printnightmare/windows-sysmon.log

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