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[Rule Tuning] Windows 3rd Party EDR Compatibility - Part 13 #5028

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Merged
merged 3 commits into from
Aug 28, 2025
Merged

[Rule Tuning] Windows 3rd Party EDR Compatibility - Part 13 #5028

merged 3 commits into from
Aug 28, 2025

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w0rk3r
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@w0rk3r w0rk3r commented Aug 27, 2025

Issue

Related (but not limited) to https://github.com/elastic/ia-trade-team/issues/498

Summary

This PR is part of a series that adds compatibility for additional data sources, including CrowdStrike, SentinelOne, Microsoft Defender for Endpoint, Endgame, and Sysmon.

To review this PR, you can use the EDR Field Compatibility Matrix, which details field compatibility for each event.category across EDR data sources.

Some changes go beyond metadata and include logic updates to optimize, simplify, or account for differences between data sources (For example, CrowdStrike uses NT Object paths for Windows paths instead of drive letters.). Please review these cases with extra attention, and don’t hesitate to ask questions.

@w0rk3r w0rk3r self-assigned this Aug 27, 2025
@w0rk3r w0rk3r added Rule: Tuning tweaking or tuning an existing rule OS: Windows windows related rules Domain: Endpoint backport: auto labels Aug 27, 2025
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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.

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tradebot-elastic commented Aug 27, 2025 •
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⛔️ Test failed

Results
  • ❌ Office Test Registry Persistence (eql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta
  • ✅ Persistence via Microsoft Outlook VBA (eql)
  • ✅ Persistence via PowerShell profile (eql)
  • ❌ Netsh Helper DLL (eql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta
  • ✅ Persistence via Microsoft Office AddIns (eql)

Samirbous
Samirbous approved these changes Aug 28, 2025
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rules/windows/persistence_ms_outlook_vba_template.toml Outdated
file where host.os.type == "windows" and event.type != "deletion" and
file.path : "C:\\Users\\*\\AppData\\Roaming\\Microsoft\\Outlook\\VbaProject.OTM"
file.name : "VbaProject.OTM" and
file.path : "*\\AppData\\Roaming\\Microsoft\\Outlook\\VbaProject.OTM"
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Suggested change
file.path : "*\\AppData\\Roaming\\Microsoft\\Outlook\\VbaProject.OTM"
file.path : ("?:\\Users\\*\\AppData\\Roaming\\Microsoft\\Outlook\\VbaProject.OTM", "\\Device\\HarddiskVolume*\\Users\\*\\AppData\\Roaming\\Microsoft\\Outlook\\VbaProject.OTM")

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@Samirbous I'm on the fence on whether this is cheaper in performance than just one generic leading wildcard, we should be good either way as we check for file.name first

terrancedejesus
terrancedejesus reviewed Aug 28, 2025
View reviewed changes
rules/windows/persistence_ms_outlook_vba_template.toml Outdated
file where host.os.type == "windows" and event.type != "deletion" and
file.path : "C:\\Users\\*\\AppData\\Roaming\\Microsoft\\Outlook\\VbaProject.OTM"
file.name : "VbaProject.OTM" and
file.path : "*\\AppData\\Roaming\\Microsoft\\Outlook\\VbaProject.OTM"
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Should we exclude outlook executable? Are we expecting manual drops/modification or the application itself?

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I think both are in scope, this activity shouldn't be common

@w0rk3r @Samirbous
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25f23ef 
Co-authored-by: Samirbous <64742097+Samirbous@users.noreply.github.com>
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tradebot-elastic commented Aug 28, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Office Test Registry Persistence (eql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta
  • ✅ Persistence via Microsoft Outlook VBA (eql)
  • ✅ Persistence via PowerShell profile (eql)
  • ❌ Netsh Helper DLL (eql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta
  • ✅ Persistence via Microsoft Office AddIns (eql)

@tradebot-elastic
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tradebot-elastic commented Aug 28, 2025 •
edited
Loading

⛔️ Test failed

Results
  • ❌ Office Test Registry Persistence (eql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta
  • ✅ Persistence via Microsoft Outlook VBA (eql)
  • ✅ Persistence via PowerShell profile (eql)
  • ❌ Netsh Helper DLL (eql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta
  • ✅ Persistence via Microsoft Office AddIns (eql)

@w0rk3r w0rk3r merged commit 79daf3f into main Aug 28, 2025
12 checks passed
@w0rk3r w0rk3r deleted the 3rd_party_edr_13 branch August 28, 2025 20:28
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Reviewers

@Samirbous Samirbous Samirbous approved these changes

@terrancedejesus terrancedejesus terrancedejesus approved these changes

@Mikaayenson Mikaayenson Awaiting requested review from Mikaayenson

@imays11 imays11 Awaiting requested review from imays11

@Aegrah Aegrah Awaiting requested review from Aegrah

@shashank-elastic shashank-elastic Awaiting requested review from shashank-elastic

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@w0rk3r w0rk3r

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backport: auto Domain: Endpoint OS: Windows windows related rules Rule: Tuning tweaking or tuning an existing rule

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@w0rk3r @tradebot-elastic @Samirbous @terrancedejesus