IMPORTANT: No additional bug fixes or documentation updates will be released for this version.
SMTP on Port 26/TCP
editSMTP on Port 26/TCP
editDetects 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-*
Severity: low
Risk score: 21
Runs every: 5 minutes
Searches indices from: now-6m (Date Math format, see also Additional look-back time)
Maximum signals per execution: 100
References:
Tags:
- Elastic
- Network
Version: 2 (version history)
Added (Elastic Stack release): 7.6.0
Last modified (Elastic Stack release): 7.6.1
Potential false positives
editServers that process email traffic may cause false positives and should be excluded from this rule as this is expected behavior.
Rule query
editnetwork.transport:tcp and destination.port:26
Threat mapping
editFramework: 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/TA0011/
-
Technique:
- Name: Exfiltration Over Alternative Protocol
- ID: T1048
- Reference URL: https://attack.mitre.org/techniques/T1048/
Rule version history
edit- Version 2 (7.6.1 release)
-
- Removed auditbeat-*, packetbeat-*, and winlogbeat-* from the rule indices.