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[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 #4222

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merged 2 commits into from
Nov 4, 2024
Merged

[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 #4222

merged 2 commits into from
Nov 4, 2024

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w0rk3r
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@w0rk3r w0rk3r commented Oct 31, 2024

Issues

Part of https://github.com/elastic/ia-trade-team/issues/242

Summary

Adjust simple (no sequence) rules to introduce support for Crowdstrike FDR. While full logic validation wasn't possible due to the lack of a test environment, the field population for each category was verified to ensure the data was correctly structured and populated as needed.

EDR field compatibility matrix may be of help to review, although the data provided by FDR is not consistent across event categories, and not even between event actions.

@w0rk3r w0rk3r added Rule: Tuning tweaking or tuning an existing rule OS: Windows windows related rules Domain: Endpoint backport: auto labels Oct 31, 2024
@w0rk3r w0rk3r self-assigned this Oct 31, 2024
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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.

Aegrah
Aegrah approved these changes Nov 1, 2024
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Just two questions. For the last 3 PRs, would it make sense changing the operators to be more efficient as well?

So changing : to like etc.

rules/windows/defense_evasion_masquerading_trusted_directory.toml
]
timestamp_override = "event.ingested"
type = "eql"

query = '''
process where host.os.type == "windows" and event.type == "start" and
process.executable : "C:\\*Program*Files*\\*.exe" and
process.executable : (
"C:\\*Program*Files*\\*.exe",
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Any reason why there are wildcards?

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To match directories that masquerade as Program Files, not the original

rules/windows/defense_evasion_masquerading_trusted_directory.toml
@@ -56,6 +61,18 @@ process where host.os.type == "windows" and event.type == "start" and
"?:\\Windows\\Downloaded Program Files\\*.exe",
"?:\\Windows\\Temp\\.opera\\????????????\\CProgram?FilesOpera*\\*.exe",
"?:\\Windows\\Temp\\.opera\\????????????\\CProgram?Files?(x86)Opera*\\*.exe"
) and
not (
event.dataset == "crowdstrike.fdr" and
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Just curious, what is this about?

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To not execute these wildcards unless the dataset is Crowdstrike, so we don't make the query more expensive by adding it

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w0rk3r commented Nov 1, 2024 •
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For the last 3 PRs, would it make sense changing the operators to be more efficient as well?

As we are dealing with multiple vendors and data sources, assuming they share a pattern when populating this data is very risky (Some may be lowercase in specific events, others, all uppercase, which can make the rules to not work). We can take a look at that in the future, but for now we don't have enough data to work on that

@w0rk3r w0rk3r merged commit 2b6116e into main Nov 4, 2024
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@w0rk3r w0rk3r deleted the crwd_2 branch November 4, 2024 14:55
protectionsmachine pushed a commit that referenced this pull request Nov 4, 2024
@w0rk3r @github-actions
[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 (#4222)
a6370ab 
Removed changes from:
- rules/windows/defense_evasion_masquerading_trusted_directory.toml
- rules/windows/defense_evasion_wsl_child_process.toml
- rules/windows/execution_apt_solarwinds_backdoor_child_cmd_powershell.toml
- rules/windows/execution_enumeration_via_wmiprvse.toml
- rules/windows/execution_initial_access_foxmail_exploit.toml
- rules/windows/execution_suspicious_cmd_wmi.toml
- rules/windows/execution_suspicious_pdf_reader.toml
- rules/windows/execution_via_compiled_html_file.toml
- rules/windows/execution_via_mmc_console_file_unusual_path.toml

(selectively cherry picked from commit 2b6116e)
protectionsmachine pushed a commit that referenced this pull request Nov 4, 2024
@w0rk3r @github-actions
[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 (#4222)
29415ab 
Removed changes from:
- rules/windows/defense_evasion_masquerading_trusted_directory.toml
- rules/windows/defense_evasion_wsl_child_process.toml
- rules/windows/execution_apt_solarwinds_backdoor_child_cmd_powershell.toml
- rules/windows/execution_enumeration_via_wmiprvse.toml
- rules/windows/execution_initial_access_foxmail_exploit.toml
- rules/windows/execution_suspicious_cmd_wmi.toml
- rules/windows/execution_suspicious_pdf_reader.toml
- rules/windows/execution_via_compiled_html_file.toml
- rules/windows/execution_via_mmc_console_file_unusual_path.toml

(selectively cherry picked from commit 2b6116e)
protectionsmachine pushed a commit that referenced this pull request Nov 4, 2024
@w0rk3r @github-actions
[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 (#4222)
24545cb 
Removed changes from:
- rules/windows/defense_evasion_masquerading_trusted_directory.toml
- rules/windows/defense_evasion_wsl_child_process.toml
- rules/windows/execution_apt_solarwinds_backdoor_child_cmd_powershell.toml
- rules/windows/execution_enumeration_via_wmiprvse.toml
- rules/windows/execution_initial_access_foxmail_exploit.toml
- rules/windows/execution_suspicious_cmd_wmi.toml
- rules/windows/execution_suspicious_pdf_reader.toml
- rules/windows/execution_via_compiled_html_file.toml
- rules/windows/execution_via_mmc_console_file_unusual_path.toml

(selectively cherry picked from commit 2b6116e)
protectionsmachine pushed a commit that referenced this pull request Nov 4, 2024
@w0rk3r @github-actions
[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 (#4222)
b586c73 
Removed changes from:
- rules/windows/defense_evasion_masquerading_trusted_directory.toml
- rules/windows/defense_evasion_wsl_child_process.toml
- rules/windows/execution_apt_solarwinds_backdoor_child_cmd_powershell.toml
- rules/windows/execution_enumeration_via_wmiprvse.toml
- rules/windows/execution_initial_access_foxmail_exploit.toml
- rules/windows/execution_suspicious_cmd_wmi.toml
- rules/windows/execution_suspicious_pdf_reader.toml
- rules/windows/execution_via_compiled_html_file.toml
- rules/windows/execution_via_mmc_console_file_unusual_path.toml

(selectively cherry picked from commit 2b6116e)
protectionsmachine pushed a commit that referenced this pull request Nov 4, 2024
@w0rk3r @github-actions
[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 (#4222)
ee1859a 
(cherry picked from commit 2b6116e)
protectionsmachine pushed a commit that referenced this pull request Nov 4, 2024
@w0rk3r @github-actions
[Rule Tuning] 3rd Party EDR - Add Crowdstrike FDR support - 3 (#4222)
9f16bc5 
(cherry picked from commit 2b6116e)
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Reviewers

@Aegrah Aegrah Aegrah approved these changes

@Samirbous Samirbous Samirbous approved these changes

@Mikaayenson Mikaayenson Awaiting requested review from Mikaayenson

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

@terrancedejesus terrancedejesus Awaiting requested review from terrancedejesus

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@w0rk3r @protectionsmachine @Samirbous @Aegrah