Sample rules
Windows Steal Authentication Certificates - ESC1 Abuse
- source: splunk
- technicques:
- T1649
Description
The following analytic detects when a new certificate is requested or granted against Active Directory Certificate Services (AD CS) using a Subject Alternative Name (SAN). It leverages Windows Security Event Codes 4886 and 4887 to identify these actions. 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 elevated privileges or persist within the environment, potentially leading to unauthorized access to sensitive information and further exploitation.
Detection logic
`wineventlog_security` EventCode IN (4886,4887) 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
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| fillnull
| 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]+)"
| eval flavor_text = case(EventCode=="4886","A suspicious certificate was requested using request ID: ".'RequestId',EventCode=="4887", "A suspicious certificate was issued using request ID: ".'RequestId'.". To revoke this certifacte use this request ID or the SSL fingerprint [".'ssl_hash'."]"), dest = upper(coalesce(req_dest_1,req_dest_2)), src = upper(coalesce(req_src,Computer))
| fields - req_*
| rename Attributes as object_attrs, EventCode as signature_id, name as signature, RequestId as ssl_serial, Requester as ssl_subject_common_name
| `windows_steal_authentication_certificates___esc1_abuse_filter`
Windows Steal Authentication Certificates - ESC1 Authentication
- source: splunk
- technicques:
- T1649
- T1550
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.
Detection logic
`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`