The following analytic identifes Event Code 4768, A
Kerberos authentication ticket (TGT) was requested, successfull occurs. This behavior has been identified to assist with detecting PetitPotam, CVE-2021-36942. Once an attacer obtains a computer certificate by abusing Active Directory Certificate Services in combination with PetitPotam, the next step would be to leverage the certificate for malicious purposes. One way of doing this is to request a Kerberos Ticket Granting Ticket using a tool like Rubeus. This request will generate a 4768 event with some unusual fields depending on the environment. This analytic will require tuning, we recommend filtering Account_Name to Domain Controllers for your environment.
- Type: TTP
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2021-08-31
- Author: Michael Haag, Mauricio Velazco, Splunk
- ID: e3ef244e-0a67-11ec-abf2-acde48001122
Kill Chain Phase
1 2 3 4 5 `wineventlog_security` EventCode=4768 Client_Address!="::1" Certificate_Thumbprint!="" Account_Name=*$ | stats count min(_time) as firstTime max(_time) as lastTime by dest, Account_Name, Client_Address, action, Message | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `petitpotam_suspicious_kerberos_tgt_request_filter`
The SPL above uses the following Macros:
petitpotam_suspicious_kerberos_tgt_request_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
The following analytic requires Event Code 4768. Ensure that it is logging no Domain Controllers and appearing in Splunk.
Known False Positives
False positives are possible if the environment is using certificates for authentication.
Associated Analytic Story
|56.0||80||70||A Kerberos TGT was requested in a non-standard manner against $dest$, potentially related to CVE-2021-36942, PetitPotam.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 1