[New Rule] Potential Malicious PowerShell Based on Alert Correlation

[w0rk3r]

Summary

Alert correlation-like rule that parses the script_block_id from the message field so we can alert when PowerShell scripts trigger multiple PowerShell rules.

Shorter description:
Identifies PowerShell script blocks associated with multiple distinct detections, indicating likely malicious behavior.

Sample Match

[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

• ❌ Potential Malicious PowerShell Based on Alert Correlation (esql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[shashank-elastic]

Add investigation guide and tag

[w0rk3r]

From what I understood, investigation guides are only required for critical alerts, otherwise we should add them as part of the release prep.

[w0rk3r]

Oh, I see. We are enforcing it for high too, I'll work on it

[terrancedejesus]

Is it optimal to aggregate on a specific user ID or host?

[w0rk3r]

As these are like UUIDs, they are not likely to repeat between different hosts, so I think we don't need that - at least for now.

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential Malicious PowerShell Based on Alert Correlation (esql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential Malicious PowerShell Based on Alert Correlation (esql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential Malicious PowerShell Based on Alert Correlation (esql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta