Detection: Windows Steal Authentication Certificates - ESC1 Authentication

Updated Date: 2026-03-17 ID: f0306acf-a6ab-437a-bbc6-8628f8d5c97e Author: Steven Dick Type: TTP Product: Splunk Enterprise Security

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.

Search

 1`wineventlog_security`
 2EventCode IN (4887)
 3Attributes="*SAN:*upn*"
 4Attributes="*CertificateTemplate:*"
 5
 6| stats
 7    count
 8    min(_time) as firstTime
 9    max(_time) as lastTime
10    values(name) as name
11    values(status) as status
12    values(Subject) as ssl_subject
13    values(SubjectKeyIdentifier) as ssl_hash
14    by Computer, EventCode, Requester, Attributes, RequestId
15
16| rex field=Attributes "(?i)CertificateTemplate:(?<object>[^\r\n]+)"
17
18| rex field=Attributes "(?i)ccm:(?<req_src>[^\r\n]+)"
19
20| rex max_match=10 field=Attributes "(?i)(upn=(?<req_user_1>[^\r\n&]+))"
21
22| rex max_match=10 field=Attributes "(?i)(dns=(?<req_dest_1>[^\r\n&]+))"
23
24| rex field=Requester "(.+\\\\)?(?<src_user>[^\r\n]+)"
25
26| rename
27    Attributes as object_attrs
28    EventCode as signature_id
29    name as signature
30    RequestId as ssl_serial
31    Requester as ssl_subject_common_name
32
33| eval user = lower(coalesce(req_user_1, req_user_2))
34
35| join user [
36    search `wineventlog_security`
37    EventCode=4768
38    CertThumbprint=*
39    
40| rename
41        TargetUserName as user
42        Computer as auth_dest
43        IpAddress as auth_src
44    
45| fields auth_src, auth_dest, user
46]
47
48| eval
49    src = upper(coalesce(auth_src, req_src)),
50    dest = upper(coalesce(auth_dest, req_dest_1, req_dest_2)),
51    risk_score = 50
52
53| eval flavor_text = case(
54    signature_id=="4887",
55    "User account [" . user . "] authenticated after a suspicious certificate was issued for it by [" . src_user . "] using certificate request ID: " . ssl_serial
56)
57
58| fields - req_* auth_*
59
60| `security_content_ctime(firstTime)`
61
62| `security_content_ctime(lastTime)`
63
64| `windows_steal_authentication_certificates___esc1_authentication_filter`

Data Source

Name	Platform	Sourcetype	Source
Windows Event Log Security 4768	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Security'`
Windows Event Log Security 4887	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Security'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_steal_authentication_certificates___esc1_authentication_filter	`search *`

windows_steal_authentication_certificates___esc1_authentication_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1649	Steal or Forge Authentication Certificates	Credential Access
T1550	Use Alternate Authentication Material	Defense Evasion

Exploitation

DE.CM

CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

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.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Possible AD CS ESC1 authentication on $dest$

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	50	ssl_hash, ssl_serial
src	system	50	ssl_hash, ssl_serial
user	user	50	ssl_hash, ssl_serial
src_user	user	50	ssl_hash, ssl_serial

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Security`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Security`	`XmlWinEventLog`

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

Source: GitHub | Version: 8