Techniques
Sample rules
Kerberos User Enumeration
- source: splunk
- technicques:
- T1589
- T1589.002
Description
The following analytic detects an unusual number of Kerberos Ticket Granting Ticket (TGT) requests for non-existing users from a single source endpoint. It leverages Event ID 4768 and identifies anomalies using the 3-sigma statistical rule. This behavior is significant as it may indicate an adversary performing a user enumeration attack against Active Directory. If confirmed malicious, the attacker could validate a list of usernames, potentially leading to further attacks such as brute force or credential stuffing, compromising the security of the environment.
Detection logic
`wineventlog_security` EventCode=4768 Status=0x6 TargetUserName!="*$"
| bucket span=2m _time
| stats dc(TargetUserName) AS unique_accounts values(TargetUserName) as tried_accounts by _time, src_ip
| eventstats avg(unique_accounts) as comp_avg , stdev(unique_accounts) as comp_std by src_ip
| eval upperBound=(comp_avg+comp_std*3)
| eval isOutlier=if(unique_accounts > 10 and unique_accounts >= upperBound, 1, 0)
| search isOutlier=1
| `kerberos_user_enumeration_filter`