Suspicious Network Connection Attempt by Root

Identifies an outbound network connection attempt followed by a session id change as the root user by the same process entity. This particular instantiation of a network connection is abnormal and should be investigated as it may indicate a potential reverse shell activity via a privileged process.

Rule type: eql

Rule indices:

logs-endpoint.events.*

Severity: medium

Risk score: 43

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Elastic
Host
Linux
Threat Detection
Command and Control

Version: 4

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Triage and analysis
### Investigating Connection Attempt by Non-SSH Root Session
Detection alerts from this rule indicate a strange or abnormal outbound connection attempt by a privileged process.  Here are some possible avenues of investigation:
- Examine unusual and active sessions using commands such as 'last -a', 'netstat -a', and 'w -a'.
- Analyze processes and command line arguments to detect anomalous process execution that may be acting as a listener.
- Analyze anomalies in the use of files that do not normally initiate connections.
- Examine processes utilizing the network that do not normally have network communication.

Rule query

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sequence by process.entity_id with maxspan=1m
[network where event.type == "start" and event.action == "connection_attempted" and user.id == "0" and
    not process.executable : ("/bin/ssh", "/sbin/ssh", "/usr/lib/systemd/systemd", "/usr/sbin/sshd")]
[process where event.action == "session_id_change" and user.id == "0" and
    not process.executable : ("/bin/ssh", "/sbin/ssh", "/usr/lib/systemd/systemd", "/usr/sbin/sshd")]

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Command and Control
- ID: TA0011
- Reference URL: https://attack.mitre.org/tactics/TA0011/
Technique:
- Name: Non-Application Layer Protocol
- ID: T1095
- Reference URL: https://attack.mitre.org/techniques/T1095/
Tactic:
- Name: Privilege Escalation
- ID: TA0004
- Reference URL: https://attack.mitre.org/tactics/TA0004/
Technique:
- Name: Abuse Elevation Control Mechanism
- ID: T1548
- Reference URL: https://attack.mitre.org/techniques/T1548/
Sub-technique:
- Name: Sudo and Sudo Caching
- ID: T1548.003
- Reference URL: https://attack.mitre.org/techniques/T1548/003/

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