Name:Unusual SSH Client Banner id:93d0f598-d65f-4c97-b030-5bb0af51a226 version:1 date:None author:Raven Tait, Splunk status:production type:Anomaly Description:The following analytic detects SSH connections presenting client banners that do not match known, common SSH client software by leveraging Zeek ssh logs.
Unusual or unknown SSH client banners may indicate custom tooling, offensive frameworks, tunneling utilities, or malware using SSH for command-and-control or lateral movement. Data_source:
how_to_implement:Zeek SSH logs must be ingested into Splunk using the latest version of Splunk Add-on for Zeek (https://splunkbase.splunk.com/app/5466).
The client field should be populated from the SSH handshake banner.
Configure the `zeek_ssh` macro to match the sourcetype used by your Zeek add-on. known_false_positives:Legitimate but uncommon SSH client software not included will generate false positives.
Review the client banner and tune the filter accordingly. References: -https://docs.zeek.org/en/master/logs/ssh.html -https://attack.mitre.org/techniques/T1021/004/ -https://attack.mitre.org/techniques/T1572/ drilldown_searches: name:'View the detection results for - "$src$"' search:'%original_detection_search% | search src = "$src$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$id.orig_h$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src$") | 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:'7d' latest_offset:'0' analytic_story:['Ingress Tool Transfer', 'Command And Control']
