SMTP on Port 26/TCPedit
Detects events that may indicate use of SMTP on TCP port 26. This port is commonly used by several popular mail transfer agents to deconflict with the default SMTP port 25. This port has also been used by a malware family called BadPatch for command and control of Windows systems.
Rule type: query
Rule indices:
- filebeat-*
- packetbeat-*
- logs-endpoint.events.*
Severity: low
Risk score: 21
Runs every: 5 minutes
Searches indices from: now-6m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
References:
Tags:
- Elastic
- Host
- Network
- Threat Detection
- Command and Control
Version: 4 (version history)
Added (Elastic Stack release): 7.6.0
Last modified (Elastic Stack release): 7.10.0
Rule authors: Elastic
Rule license: Elastic License
Potential false positivesedit
Servers that process email traffic may cause false positives and should be excluded from this rule as this is expected behavior.
Rule queryedit
event.category:(network or network_traffic) and network.transport:tcp and (destination.port:26 or (event.dataset:zeek.smtp and destination.port:26))
Threat mappingedit
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Command and Control
- ID: TA0011
- Reference URL: https://attack.mitre.org/tactics/TA0011/
-
Technique:
- Name: Commonly Used Port
- ID: T1043
- Reference URL: https://attack.mitre.org/techniques/T1043/
-
Tactic:
- Name: Exfiltration
- ID: TA0010
- Reference URL: https://attack.mitre.org/tactics/TA0010/
-
Technique:
- Name: Exfiltration Over Alternative Protocol
- ID: T1048
- Reference URL: https://attack.mitre.org/techniques/T1048/
Rule version historyedit
- Version 4 (7.10.0 release)
-
- Formatting only
- Version 3 (7.9.0 release)
-
-
Updated query, changed from:
network.transport:tcp and destination.port:26
-
- Version 2 (7.6.1 release)
-
- Removed auditbeat-*, packetbeat-*, and winlogbeat-* from the rule indices.