[New Rule] Potential SSH Reverse Port Forwarding

[w0rk3r]

Issues

Part of https://github.com/elastic/ia-trade-team/issues/888

Summary

Identifies the use of Windows OpenSSH or Plink to create a reverse SSH port forward or reverse dynamic SOCKS proxy. Adversaries may abuse reverse forwarding to expose an internal service or proxy listener through an external SSH server, establishing an outbound tunnel that bypasses direct inbound connectivity controls.

References:

• https://thedfirreport.com/2025/11/04/from-bing-search-to-ransomware-bumblebee-and-adaptixc2-deliver-akira-2/
• https://thedfirreport.com/2023/10/30/netsupport-intrusion-results-in-domain-compromise/

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential SSH Reverse Port Forwarding (eql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[github-actions]

Rule: New - Guidelines

These guidelines serve as a reminder set of considerations when proposing a new rule.

Documentation and Context

• Detailed description of the rule.
• List any new fields required in ECS/data sources.
• Link related issues or PRs.
• Include references.

Rule Metadata Checks

• creation_date matches the date of creation PR initially merged.
• min_stack_version should support the widest stack versions.
• name and description should be descriptive and not include typos.
• query should be inclusive, not overly exclusive, considering performance for diverse environments. Non ecs fields should be added to non-ecs-schema.json if not available in an integration.
• min_stack_comments and min_stack_version should be included if the rule is only compatible starting from a specific stack version.
• index pattern should be neither too specific nor too vague, ensuring it accurately matches the relevant data stream (e.g., use logs-endpoint.process-* for process data).
• integration should align with the index. If the integration is newly introduced, ensure the manifest, schemas, and new_rule.yaml template are updated.
• setup should include the necessary steps to configure the integration.
• note should include any additional information (e.g. Triage and analysis investigation guides, timeline templates).
• tags should be relevant to the threat and align/added to the EXPECTED_RULE_TAGS in the definitions.py file.
• threat, techniques, and subtechniques should map to ATT&CK always if possible.

New BBR Rules

• building_block_type should be included if the rule is a building block and the rule should be located in the rules_building_block folder.
• bypass_bbr_timing should be included if adding custom lookback timing to the rule.

Testing and Validation

• Provide evidence of testing and detecting the expected threat.
• Check for existence of coverage to prevent duplication.

[Copilot]

Pull request overview

Adds a new Windows EQL detection rule to identify reverse SSH port forwarding / reverse dynamic forwarding activity via Windows OpenSSH (ssh.exe) or PuTTY Plink (plink.exe), including an investigation guide and investigation transforms to support triage and scoping.

Changes:

• Introduces a new Windows rule targeting reverse port-forwarding indicators (-R / RemoteForward) for OpenSSH and Plink.
• Adds an investigation guide plus investigate transforms for process context, recurrence on host, and hash-based scoping.
• Maps the detection to relevant MITRE ATT&CK tactics/techniques (Proxy/External Proxy, Protocol Tunneling, Remote Services/SSH).

[eric-forte-elastic]

I think the current logic for the regex and process.args filters could miss the compact form:
ssh.exe -fNR2222:127.0.0.1:3389 user@host

[terrancedejesus]

++

[w0rk3r]

Updated the regex to account for this, thanks!

[eric-forte-elastic]

Small comment and I think Copilot suggestion might be valid.

Otherwise LGTM 👍

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential SSH Reverse Port Forwarding (eql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential SSH Reverse Port Forwarding (eql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta