splunk_escuAnomaly

Windows SIP WinVerifyTrust Failed Trust Validation

The following analytic detects failed trust validation attempts using Windows Event Log - CAPI2 (CryptoAPI 2). It specifically triggers on EventID 81, which indicates that "The digital signature of the object did not verify." This detection leverages the CAPI2 Operational log to identify instances where digital signatures fail to validate. Monitoring this activity is crucial as it can indicate attempts to execute untrusted or potentially malicious binaries. If confirmed malicious, this activity could allow attackers to bypass security controls and execute unauthorized code, leading to potential system compromise.

MITRE ATT&CK

T1553.003

Detection Query

`capi2_operational` EventID=81 "The digital signature of the object did not verify."
  | xmlkv UserData_Xml
  | stats count min(_time) as firstTime max(_time) as lastTime
    BY Computer, UserData_Xml
  | rename Computer as dest
  | `windows_sip_winverifytrust_failed_trust_validation_filter`

Author

Michael Haag, Splunk

Created

2026-03-10

Data Sources

Windows Event Log CAPI2 81

References

Tags

Subvert Trust Controls SIP and Trust Provider Hijacking

Raw Content

name: Windows SIP WinVerifyTrust Failed Trust Validation
id: 6ffc7f88-415b-4278-a80d-b957d6539e1a
version: 7
date: '2026-03-10'
author: Michael Haag, Splunk
status: production
type: Anomaly
data_source:
    - Windows Event Log CAPI2 81
description: The following analytic detects failed trust validation attempts using Windows Event Log - CAPI2 (CryptoAPI 2). It specifically triggers on EventID 81, which indicates that "The digital signature of the object did not verify." This detection leverages the CAPI2 Operational log to identify instances where digital signatures fail to validate. Monitoring this activity is crucial as it can indicate attempts to execute untrusted or potentially malicious binaries. If confirmed malicious, this activity could allow attackers to bypass security controls and execute unauthorized code, leading to potential system compromise.
search: |-
    `capi2_operational` EventID=81 "The digital signature of the object did not verify."
      | xmlkv UserData_Xml
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY Computer, UserData_Xml
      | rename Computer as dest
      | `windows_sip_winverifytrust_failed_trust_validation_filter`
how_to_implement: To implement this analytic, one will need to enable the Microsoft-Windows-CAPI2/Operational log within the Windows Event Log. Note this is a debug log for many purposes, and the analytic only focuses in on EventID 81. Review the following gist for additional enabling information.
known_false_positives: False positives may be present in some instances of legitimate binaries with invalid signatures. Filter as needed.
references:
    - https://attack.mitre.org/techniques/T1553/003/
    - https://specterops.io/wp-content/uploads/sites/3/2022/06/SpecterOps_Subverting_Trust_in_Windows.pdf
    - https://github.com/gtworek/PSBits/tree/master/SIP
    - https://github.com/mattifestation/PoCSubjectInterfacePackage
    - https://pentestlab.blog/2017/11/06/hijacking-digital-signatures/
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: Failed trust validation via the CryptoAPI 2 on $dest$ for a binary.
    risk_objects:
        - field: dest
          type: system
          score: 20
    threat_objects: []
tags:
    analytic_story:
        - Subvert Trust Controls SIP and Trust Provider Hijacking
    asset_type: Endpoint
    atomic_guid: []
    mitre_attack_id:
        - T1553.003
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1553.003/sip/capi2-operational.log
          source: XmlWinEventLog:Microsoft-Windows-CAPI2/Operational
          sourcetype: XmlWinEventLog