Protocol or Port Mismatch

Name:Protocol or Port Mismatch
id:54dc1265-2f74-4b6d-b30d-49eb506a31b3
version:8
date:2025-05-27
author:Rico Valdez, Splunk
status:production
type:Anomaly
Description:The following analytic identifies network traffic where the higher layer protocol does not match the expected port, such as non-HTTP traffic on TCP port 80. It leverages data from network traffic inspection technologies like Bro or Palo Alto Networks firewalls. This activity is significant because it may indicate attempts to bypass firewall restrictions or conceal malicious communications. If confirmed malicious, this behavior could allow attackers to evade detection, maintain persistence, or exfiltrate data through commonly allowed ports, posing a significant threat to network security.
Data_source:

• -Cisco Secure Firewall Threat Defense Connection Event

search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Network_Traffic where (All_Traffic.app=dns NOT All_Traffic.dest_port=53) OR ((All_Traffic.app=web-browsing OR All_Traffic.app=http) NOT (All_Traffic.dest_port=80 OR All_Traffic.dest_port=8080 OR All_Traffic.dest_port=8000)) OR (All_Traffic.app=ssl NOT (All_Traffic.dest_port=443 OR All_Traffic.dest_port=8443)) OR (All_Traffic.app=smtp NOT All_Traffic.dest_port=25) by All_Traffic.src_ip, All_Traffic.dest_ip, All_Traffic.app, All_Traffic.dest_port All_Traffic.transport All_Traffic.action All_Traffic.rule |`security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `drop_dm_object_name("All_Traffic")`
| `protocol_or_port_mismatch_filter`

how_to_implement:Running this search properly requires a technology that can inspect network traffic and identify common protocols. Technologies such as Zeek, Cisco Secure Firewall or Palo Alto Networks firewalls are examples that will identify protocols via inspection, and not just assume a specific protocol based on the transport protocol and ports.
known_false_positives:Some false positive could occur with some applications that change their default communication port for an added layer of obscurity.
References:
drilldown_searches:
 name:'View the detection results for - "$src_ip$"'
 search:'%original_detection_search% | search src_ip = "$src_ip$"'
 earliest_offset:'$info_min_time$'
 latest_offset:'$info_max_time$'
 name:'View risk events for the last 7 days for - "$src_ip$"'
 search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src_ip$") 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:
    - 'Prohibited Traffic Allowed or Protocol Mismatch'
    - 'Command And Control'
    - 'Cisco Secure Firewall Threat Defense Analytics'
  asset_type:Endpoint
  mitre_attack_id:
    - 'T1048.003'
  product:
    - 'Splunk Enterprise'
    - 'Splunk Enterprise Security'
    - 'Splunk Cloud'
  security_domain:network

tests:
 name:'Cisco Secure Firewall True Positive Test'
 attack_data:
  data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/cisco_secure_firewall_threat_defense/connection_event/connection_events.log
  source: not_applicable
  sourcetype: cisco:sfw:estreamer
manual_test:None