Name:Suspicious Kerberos Service Ticket Request id:8b1297bc-6204-11ec-b7c4-acde48001122 version:5 date:2024-09-30 author:Mauricio Velazco, Splunk status:production type:TTP Description:The following analytic detects suspicious Kerberos Service Ticket (TGS) requests where the requesting account name matches the service name, potentially indicating an exploitation attempt of CVE-2021-42278 and CVE-2021-42287. This detection leverages Event ID 4769 from Domain Controller and Kerberos events. Such activity is significant as it may represent an adversary attempting to escalate privileges by impersonating a domain controller. If confirmed malicious, this could allow an attacker to take control of the domain controller, leading to complete domain compromise and unauthorized access to sensitive information. Data_source:
-Windows Event Log Security 4769
search:`wineventlog_security` EventCode=4769 | eval isSuspicious = if(lower(ServiceName) = lower(mvindex(split(TargetUserName,"@"),0)),1,0) | where isSuspicious = 1 | rename Computer as dest| rename TargetUserName as user | table _time, dest, src_ip, user, ServiceName, Error_Code, isSuspicious | `suspicious_kerberos_service_ticket_request_filter`
how_to_implement:To successfully implement this search, you need to be ingesting Domain Controller and Kerberos events. The Advanced Security Audit policy setting `Audit Kerberos Authentication Service` within `Account Logon` needs to be enabled. known_false_positives:We have tested this detection logic with ~2 million 4769 events and did not identify false positives. However, they may be possible in certain environments. Filter as needed. References: -https://exploit.ph/cve-2021-42287-cve-2021-42278-weaponisation.html -https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42278 -https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42287 -https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-sfu/02636893-7a1f-4357-af9a-b672e3e3de13 drilldown_searches: name:'View the detection results for - "$dest$"' search:'%original_detection_search% | search dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") 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:'$info_max_time$' tags: analytic_story: - 'sAMAccountName Spoofing and Domain Controller Impersonation' - 'Active Directory Kerberos Attacks' - 'Active Directory Privilege Escalation' asset_type:Endpoint confidence:60 cve: - 'CVE-2021-42287' - 'CVE-2021-42278' impact:100 message:A suspicious Kerberos Service Ticket was requested by $user$ on host $dest$ mitre_attack_id: - 'T1078' - 'T1078.002' observable: name:'dest' type:'Endpoint' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'EventCode' - 'Service_Name' - 'Account_Name' - 'Client_Address' - 'Failure_Code' risk_score:60 security_domain:endpoint
