[Rule Tuning] Remote File Download via PowerShell

[w0rk3r]

Issues

Resolves #4974

Summary

Adjusts the logic to exclude multiple FPs

[github-actions]

Rule: Tuning - Guidelines

These guidelines serve as a reminder set of considerations when tuning an existing rule.

Documentation and Context

• Detailed description of the suggested changes.
• Provide example JSON data or screenshots.
• Provide evidence of reducing benign events mistakenly identified as threats (False Positives).
• Provide evidence of enhancing detection of true threats that were previously missed (False Negatives).
• Provide evidence of optimizing resource consumption and execution time of detection rules (Performance).
• Provide evidence of specific environment factors influencing customized rule tuning (Contextual Tuning).
• Provide evidence of improvements made by modifying sensitivity by changing alert triggering thresholds (Threshold Adjustments).
• Provide evidence of refining rules to better detect deviations from typical behavior (Behavioral Tuning).
• Provide evidence of improvements of adjusting rules based on time-based patterns (Temporal Tuning).
• Provide reasoning of adjusting priority or severity levels of alerts (Severity Tuning).
• Provide evidence of improving quality integrity of our data used by detection rules (Data Quality).
• Ensure the tuning includes necessary updates to the release documentation and versioning.

Rule Metadata Checks

• updated_date matches the date of tuning PR 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. Review to ensure the original intent of the rule is maintained.

Testing and Validation

• Validate that the tuned rule's performance is satisfactory and does not negatively impact the stack.
• Ensure that the tuned rule has a low false positive rate.

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Remote File Download via PowerShell (eql)
  • stack_validation_failed: no_alerts - 0 alerts

[Aegrah]

Won't *.* filter out too much?

[w0rk3r]

I don't think so, every domain has dots

[Samirbous]

the Users Temp exclusion are too brittle

[w0rk3r]

Discussed this one via Slack, but for other reviewers: I agree, but this one is the best shot we have to exclude some noisy activity without including another event in the sequence start, which would have significant performance problems.

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Remote File Download via PowerShell (eql)
  • stack_validation_failed: no_alerts - 0 alerts

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Remote File Download via PowerShell (eql)
  • stack_validation_failed: no_alerts - 0 alerts

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Remote File Download via PowerShell (eql)
  • stack_validation_failed: no_alerts - 0 alerts