spoolsv_suspicious_process_access.yml

name: Spoolsv Suspicious Process Access
id: 799b606e-da81-11eb-93f8-acde48001122
version: 1
date: '2021-07-01'
author: Mauricio Velazco, Michael Haag, Teoderick Contreras, Splunk
status: production
type: TTP
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.
data_source:
- Sysmon Event ID 1
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 dest SourceImage
  TargetImage GrantedAccess CallTrace  EventCode ProcessID| `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)` | `spoolsv_suspicious_process_access_filter`'
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.
known_false_positives: Unknown. Filter as needed.
references:
- https://github.com/cube0x0/impacket/commit/73b9466c17761384ece11e1028ec6689abad6818
- https://www.truesec.com/hub/blog/fix-for-printnightmare-cve-2021-1675-exploit-to-keep-your-print-servers-running-while-a-patch-is-not-available
- https://www.truesec.com/hub/blog/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
tags:
  analytic_story:
  - PrintNightmare CVE-2021-34527
  asset_type: Endpoint
  confidence: 90
  cve:
  - CVE-2021-34527
  impact: 80
  message: $SourceImage$ was GrantedAccess open access to $TargetImage$ on endpoint
    $dest$. This behavior is suspicious and related to PrintNightmare.
  mitre_attack_id:
  - T1068
  observable:
  - name: dest
    type: Endpoint
    role:
    - Victim
  - name: ProcessID
    type: Process
    role:
    - Parent Process
  - name: TargetImage
    type: Process Name
    role:
    - Target
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - SourceImage
  - TargetImage
  - GrantedAccess
  - CallTrace
  - EventCode
  risk_score: 72
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1547.012/printnightmare/windows-sysmon.log
    source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
    sourcetype: xmlwineventlog