MacOS detection rules tuning

[DefSecSentinel]

Associated Issue

#4456

Summary

Syncs and tunes macOS detection rules based on endpoint-rules logic and 90-day telemetry analysis.

Changes

Endpoint Rules Sync (5 rules)

Rule	Fix
Bifrost Kerberos	Fixed broken query logic - parentheses grouping was incorrect
Osascript Phishing	Added authenticate pattern, NinjaRMM exclusion, sudo parent exclusion
SCP Privacy Bypass	Changed 127.0.0.1 to 127.0.0.? pattern to catch alternate loopback bypass
Kext Unload	Added EndpointSecurity wildcard pattern
Safari Settings	Changed from broad catch-all to targeted dangerous settings

Telemetry-Based Tuning (1 rule)

Rule	Alerts (90d)	Fix
Hosts File Modified	5,074	Added Parallels Desktop exclusion for macOS

Context

These detection rules have counterparts in the endpoint-rules repository that are regularly tuned. This PR brings the detection-rules versions up to parity with the endpoint-rules logic and reduces false positives based on telemetry analysis.

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential Kerberos Attack via Bifrost (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Prompt for Credentials with Osascript (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Modification of Safari Settings via Defaults Command (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ✅ Attempt to Unload Elastic Endpoint Security Kernel Extension (eql)
• ✅ Hosts File Modified (eql)
• ❌ Potential Privacy Control Bypass via Localhost Secure Copy (eql)
  • stack_validation_failed: no_alerts - 0 alerts

[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

• ❌ Potential Kerberos Attack via Bifrost (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Prompt for Credentials with Osascript (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Modification of Safari Settings via Defaults Command (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ✅ Attempt to Unload Elastic Endpoint Security Kernel Extension (eql)
• ✅ Hosts File Modified (eql)
• ❌ Potential Privacy Control Bypass via Localhost Secure Copy (eql)
  • stack_validation_failed: no_alerts - 0 alerts

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential Kerberos Attack via Bifrost (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Prompt for Credentials with Osascript (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Modification of Safari Settings via Defaults Command (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ✅ Attempt to Unload Elastic Endpoint Security Kernel Extension (eql)
• ✅ Hosts File Modified (eql)
• ❌ Potential Privacy Control Bypass via Localhost Secure Copy (eql)
  • stack_validation_failed: no_alerts - 0 alerts

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Potential Kerberos Attack via Bifrost (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Prompt for Credentials with Osascript (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ❌ Modification of Safari Settings via Defaults Command (eql)
  • stack_validation_failed: no_alerts - 0 alerts
• ✅ Attempt to Unload Elastic Endpoint Security Kernel Extension (eql)
• ✅ Hosts File Modified (eql)
• ❌ Potential Privacy Control Bypass via Localhost Secure Copy (eql)
  • stack_validation_failed: no_alerts - 0 alerts