Telnet Port Activityedit

Detects network events that may indicate the use of Telnet traffic. Telnet is commonly used by system administrators to remotely control older or embedded systems using the command line shell. It should almost never be directly exposed to the Internet, as it is frequently targeted and exploited by threat actors as an initial access or back-door vector. As a plain-text protocol, it may also expose usernames and passwords to anyone capable of observing the traffic.

Rule type: query

Rule indices:

  • filebeat-*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum signals per execution: 100


  • Elastic
  • Network

Version: 2 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.6.1

Potential false positivesedit

IoT (Internet of Things) devices and networks may use telnet and can be excluded if desired. Some business workflows may use Telnet for administration of older devices. These often have a predictable behavior. Telnet activity involving an unusual source or destination may be more suspicious. Telnet activity involving a production server that has no known associated Telnet workflow or business requirement is often suspicious.

Rule queryedit

network.transport:tcp and destination.port:23

Threat mappingedit


Rule version historyedit

Version 2 (7.6.1 release)
  • Removed auditbeat-*, packetbeat-*, and winlogbeat-* from the rule indices.