Elastic Security Detection Rules

Accepted Default Telnet Port Connection

Last updated 7 months ago on 2025-01-15
Created 6 years ago on 2020-02-18

About

This rule 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 backdoor vector. As a plain-text protocol, it may also expose usernames and passwords to anyone capable of observing the traffic.
Tags
Domain: EndpointUse Case: Threat DetectionTactic: Command and ControlTactic: Lateral MovementTactic: Initial AccessData Source: PAN-OSLanguage: kuery
Severity
medium
Risk Score
47
MITRE ATT&CK™

Command and Control (TA0011)(opens in a new tab or window)

Lateral Movement (TA0008)(opens in a new tab or window)

↳ Remote Services (T1021)(opens in a new tab or window)

Initial Access (TA0001)(opens in a new tab or window)

↳ Exploit Public-Facing Application (T1190)(opens in a new tab or window)

False Positive Examples
IoT (Internet of Things) devices and networks may use telnet and can be excluded if desired. Some business work-flows 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 work-flow or business requirement is often suspicious.
License
Elastic License v2(opens in a new tab or window)

Definition

Rule Type
Query (Kibana Query Language)
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
packetbeat-*auditbeat-*filebeat-*logs-network_traffic.*logs-panw.panos*
Related Integrations

network_traffic(opens in a new tab or window)

panw(opens in a new tab or window)

Query
(event.dataset:network_traffic.flow or event.category:(network or network_traffic))
    and event.type:connection and not event.action:(
        flow_dropped or flow_denied or denied or deny or
        flow_terminated or timeout or Reject or network_flow)
    and destination.port:23

Install detection rules in Elastic Security

Detect Accepted Default Telnet Port Connection in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(opens in a new tab or window).