Name:Cisco Secure Firewall - SSH Connection to Non-Standard Port id:9b0c2d3e-4f5a-6b7c-8d9e-0f1a2b3c4d5e version:5 date:None author:Nasreddine Bencherchali, Michael Haag, Splunk status:production type:Anomaly Description:This analytic detects inbound SSH connections to non-standard ports on network devices using Cisco Secure Firewall Intrusion Events. APT actors have been observed enabling SSH servers on high, non-default TCP ports to maintain encrypted remote access to compromised network infrastructure.
This detection leverages Snort signature 65369 to identify SSH protocol traffic on unusual ports, which may indicate persistence mechanisms or backdoor access established by threat actors.
Data_source:
search:`cisco_secure_firewall` EventType=IntrusionEvent signature_id=65369 | fillnull | stats dc(signature_id) as unique_signature_count values(signature_id) as signature_id values(signature) as signature values(class_desc) as class_desc values(MitreAttackGroups) as MitreAttackGroups values(InlineResult) as InlineResult values(InlineResultReason) as InlineResultReason values(src) as src values(dest_port) as dest_port values(rule) as rule values(transport) as transport values(app) as app min(_time) as firstTime max(_time) as lastTime by dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `cisco_secure_firewall___ssh_connection_to_non_standard_port_filter`
how_to_implement:This search requires Cisco Secure Firewall Threat Defense Logs, which
includes the FileEvent EventType. This search uses an input macro named `cisco_secure_firewall`.
We strongly recommend that you specify your environment-specific configurations
(index, source, sourcetype, etc.) for Cisco Secure Firewall Threat Defense logs. Replace the macro definition
with configurations for your Splunk environment. The search also uses a post-filter
macro designed to filter out known false positives.
The logs are to be ingested using the Splunk Add-on for Cisco Security Cloud (https://splunkbase.splunk.com/app/7404).
The malware & file access policy must also enable logging.
known_false_positives:No false positives have been identified yet.
References: -https://www.cisa.gov/news-events/cybersecurity-advisories/aa25-239a 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 - "$src$"' 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:['Cisco Secure Firewall Threat Defense Analytics', 'Salt Typhoon']
