Connection to Internal Network via Telnet
editConnection to Internal Network via Telnet
editTelnet provides a command line interface for communication with a remote device or server. This rule identifies Telnet network connections to non-publicly routable IP addresses.
Rule type: eql
Rule indices:
- auditbeat-*
- logs-endpoint.events.*
Severity: medium
Risk score: 47
Runs every: 5 minutes
Searches indices from: now-9m (Date Math format, see also Additional look-back time)
Maximum alerts per execution: 100
Tags:
- Elastic
- Host
- Linux
- Threat Detection
- Lateral Movement
Version: 4 (version history)
Added (Elastic Stack release): 7.8.0
Last modified (Elastic Stack release): 7.10.0
Rule authors: Elastic
Rule license: Elastic License
Potential false positives
editTelnet can be used for both benign or malicious purposes. Telnet is included by default in some Linux distributions, so its presence is not inherently suspicious. The use of Telnet to manage devices remotely has declined in recent years in favor of more secure protocols such as SSH. Telnet usage by non-automated tools or frameworks may be suspicious.
Rule query
editsequence by process.entity_id [process where process.name == "telnet" and event.type == "start"] [network where process.name == "telnet" and cidrmatch(destination.ip, "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16", "FE80::/10") and not cidrmatch(destination.ip, "127.0.0.0/8", "::1/128")]
Threat mapping
editFramework: MITRE ATT&CKTM
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Tactic:
- Name: Lateral Movement
- ID: TA0008
- Reference URL: https://attack.mitre.org/tactics/TA0008/
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Technique:
- Name: Remote Services
- ID: T1021
- Reference URL: https://attack.mitre.org/techniques/T1021/
Rule version history
edit- Version 4 (7.10.0 release)
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-
Updated query, changed from:
event.category:network and event.type:(connection or start) and process.name:telnet and destination.ip:((10.0.0.0/8 or 172.16.0.0/12 or 192.168.0.0/16 or "FE80::/10") and not (127.0.0.0/8 or "::1/128"))
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- Version 3 (7.9.1 release)
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- Formatting only
- Version 2 (7.9.0 release)
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-
Updated query, changed from:
event.action:("connected-to" or "network_flow") and process.name:telnet and destination.ip:((10.0.0.0/8 or 172.16.0.0/12 or 192.168.0.0/16 or "FE80::/10") and not (127.0.0.0/8 or "::1/128"))
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