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Unusual SSH Client Banner

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…

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.

Detection logic

Detection requirements

Platform
ESXiLinuxmacOSWindows

The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.

Log source category
zeek_ssh

Known benign triggers

  • Legitimate but uncommon SSH client software not included will generate false positives. Review the client banner and tune the filter accordingly.

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