Windows Steal Authentication Certificates - ESC1 Authentication

name: Windows Steal Authentication Certificates - ESC1 Authentication
id: f0306acf-a6ab-437a-bbc6-8628f8d5c97e
version: 8
date: '2026-03-17'
author: Steven Dick
status: production
type: TTP
description: The following analytic detects when a suspicious certificate with a Subject Alternative Name (SAN) is issued using Active Directory Certificate Services (AD CS) and then immediately used for authentication. This detection leverages Windows Security Event Logs, specifically EventCode 4887, to identify the issuance and subsequent use of the certificate. This activity is significant because improperly configured certificate templates can be exploited for privilege escalation and environment compromise. If confirmed malicious, an attacker could gain unauthorized access, escalate privileges, and potentially compromise the entire environment.
data_source:
    - Windows Event Log Security 4887
    - Windows Event Log Security 4768
search: |-
    `wineventlog_security`
    EventCode IN (4887)
    Attributes="*SAN:*upn*"
    Attributes="*CertificateTemplate:*"
    | stats
        count
        min(_time) as firstTime
        max(_time) as lastTime
        values(name) as name
        values(status) as status
        values(Subject) as ssl_subject
        values(SubjectKeyIdentifier) as ssl_hash
        by Computer, EventCode, Requester, Attributes, RequestId
    | rex field=Attributes "(?i)CertificateTemplate:(?<object>[^\r\n]+)"
    | rex field=Attributes "(?i)ccm:(?<req_src>[^\r\n]+)"
    | rex max_match=10 field=Attributes "(?i)(upn=(?<req_user_1>[^\r\n&]+))"
    | rex max_match=10 field=Attributes "(?i)(dns=(?<req_dest_1>[^\r\n&]+))"
    | rex field=Requester "(.+\\\\)?(?<src_user>[^\r\n]+)"
    | rename
        Attributes as object_attrs
        EventCode as signature_id
        name as signature
        RequestId as ssl_serial
        Requester as ssl_subject_common_name
    | eval user = lower(coalesce(req_user_1, req_user_2))
    | join user [
        search `wineventlog_security`
        EventCode=4768
        CertThumbprint=*
        | rename
            TargetUserName as user
            Computer as auth_dest
            IpAddress as auth_src
        | fields auth_src, auth_dest, user
    ]
    | eval
        src = upper(coalesce(auth_src, req_src)),
        dest = upper(coalesce(auth_dest, req_dest_1, req_dest_2)),
        risk_score = 50
    | eval flavor_text = case(
        signature_id=="4887",
        "User account [" . user . "] authenticated after a suspicious certificate was issued for it by [" . src_user . "] using certificate request ID: " . ssl_serial
    )
    | fields - req_* auth_*
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `windows_steal_authentication_certificates___esc1_authentication_filter`
how_to_implement: To implement this analytic, enhanced Audit Logging must be enabled on AD CS and within Group Policy Management for CS server. See Page 115 of first reference. Recommend throttle correlation by RequestId/ssl_serial at minimum.
known_false_positives: False positives may be generated in environments where administrative users or processes are allowed to generate certificates with Subject Alternative Names for authentication. Sources or templates used in these processes may need to be tuned out for accurate function.
references:
    - https://specterops.io/wp-content/uploads/sites/3/2022/06/Certified_Pre-Owned.pdf
    - https://github.com/ly4k/Certipy#esc1
    - https://pentestlaboratories.com/2021/11/08/threat-hunting-certificate-account-persistence/
drilldown_searches:
    - name: View the detection results for - "$src$" and "$dest$"
      search: '%original_detection_search% | search  src = "$src$" dest = "$dest$" src_user = "$src_user$" user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$src$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src$", "$dest$", "$src_user$", "$user$") 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: Possible AD CS ESC1 authentication on $dest$
    risk_objects:
        - field: src
          type: system
          score: 50
        - field: dest
          type: system
          score: 50
        - field: src_user
          type: user
          score: 50
        - field: user
          type: user
          score: 50
    threat_objects:
        - field: ssl_hash
          type: tls_hash
        - field: ssl_serial
          type: certificate_serial
tags:
    analytic_story:
        - Windows Certificate Services
        - Compromised Windows Host
    asset_type: Endpoint
    mitre_attack_id:
        - T1649
        - T1550
    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/T1649/certify_abuse/certify_esc1_abuse_winsecurity.log
          source: XmlWinEventLog:Security
          sourcetype: XmlWinEventLog