[New Rule] SMB (Windows File Sharing) Activity from the Internet

[eric-forte-elastic]

Pull Request

Issue link(s):

Summary - What I changed

Adds a new new_terms network detection rule that fires when a public IP reaches an internal host on TCP 139 or 445 (SMB/CIFS). This is the inbound counterpart to initial_access_smb_windows_file_sharing_activity_to_the_internet.toml; the two rules are mutually exclusive by design. Inbound SMB from the Internet is a direct precondition for EternalBlue (MS17-010) and the broader SMB RCE vulnerability class. new_terms suppression on source.ip with a 5-day window collapses repeat Internet scanners to one alert per new external source.

Corelight and pfSense are added as primary data sources alongside the existing network_traffic, panw, and zeek integrations.

Note

pfSense and Corelight support need to be merged first before this rule can be added.

How To Test

Unit Tests, shared stack data, and RTA.

Checklist

• Added a label for the type of pr: bug, enhancement, schema, maintenance, Rule: New, Rule: Deprecation, Rule: Tuning, Hunt: New, or Hunt: Tuning so guidelines can be generated
• Added the meta:rapid-merge label if planning to merge within 24 hours
• Secret and sensitive material has been managed correctly
• Automated testing was updated or added to match the most common scenarios
• Documentation and comments were added for features that require explanation

Contributor checklist

• Have you signed the contributor license agreement?
• Have you followed the contributor guidelines?

[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.

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ SMB (Windows File Sharing) Activity from the Internet (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ SMB (Windows File Sharing) Activity from the Internet (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[Copilot]

Pull request overview

Adds a new network new_terms detection rule to alert on inbound SMB (TCP/139,445) from public IPs to RFC1918 destinations, intended to surface Internet scanning/exploitation attempts while suppressing repeat sources.

Changes:

• Introduces a new new_terms rule for “SMB (Windows File Sharing) Activity from the Internet” with public-source filtering and RFC1918 destination scoping.
• Adds an investigation guide (triage, FP guidance, response, setup) and configures new_terms suppression on source.ip with a 5-day history window.

[tradebot-elastic]

Starting the rule tests ...

[bryans3c]

Solid one!

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ SMB (Windows File Sharing) Activity from the Internet (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta