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splunk-security_content/dev/endpoint/spoolsv_spawning_rundll32.yml
2023-01-20 13:24:15 +01:00

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YAML

name: Spoolsv Spawning Rundll32
id: 15d905f6-da6b-11eb-ab82-acde48001122
version: 2
date: '2021-07-01'
author: Mauricio Velazco, Michael Haag, Splunk
status: production
type: TTP
description: The following analytic identifies a suspicious child process, `rundll32.exe`,
with no command-line arguments being spawned from `spoolsv.exe`. This was identified
during our testing of CVE-2021-34527 previously (CVE-2021-1675) or PrintNightmare.
Typically, this is not normal behavior for `spoolsv.exe` to spawn a process. During
triage, isolate the endpoint and review for source of exploitation. Capture any
additional file modification events.
data_source:
- Sysmon Event ID 1
search:
selection1:
ParentImage: spoolsv.exe
condition: selection1
how_to_implement: To successfully implement this search you need to be ingesting information
on process that include the name of the process responsible for the changes from
your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition,
confirm the latest CIM App 4.20 or higher is installed and the latest TA for the
endpoint product.
known_false_positives: Limited false positives have been identified. There are limited
instances where `rundll32.exe` may be spawned by a legitimate print driver.
references:
- 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: $parent_process$ has spawned $process_name$ on endpoint $ComputerName$.
This behavior is suspicious and related to PrintNightmare.
mitre_attack_id:
- T1547.012
- T1547
observable:
- name: dest
type: Endpoint
role:
- Victim
- name: parent_process_id
type: Process
role:
- Parent Process
- Attacker
- name: process_id
type: Process
role:
- Child Process
product:
- Splunk Enterprise
- Splunk Enterprise Security
- Splunk Cloud
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