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Merged
merged 9 commits into from
Aug 18, 2025
Merged

[New] Command Line Obfuscation via Whitespace Padding #4860

merged 9 commits into from
Aug 18, 2025

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Samirbous
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@Samirbous Samirbous self-assigned this Jun 30, 2025
@Samirbous Samirbous added Rule: New Proposal for new rule OS: Windows windows related rules labels Jun 30, 2025
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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
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Starting the rule tests ...

@Samirbous Samirbous requested a review from w0rk3r June 30, 2025 10:07
@tradebot-elastic
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Starting the rule tests ...

@Samirbous Samirbous requested a review from Aegrah June 30, 2025 10:10
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Starting the rule tests ...

@Samirbous
Update and rename defense_evasion_whitespace_padding_command_line.tom…
d982e64 
…l to defense_evasion_whitespace_padding_command_line.toml
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Starting the rule tests ...

@Samirbous Samirbous changed the title [New] Command Line Obfuscation via Whitespace Padding" [New] Command Line Obfuscation via Whitespace Padding Jun 30, 2025
Aegrah
Aegrah approved these changes Jun 30, 2025
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rules/cross-platform/defense_evasion_whitespace_padding_command_line.toml Outdated
@@ -0,0 +1,128 @@
[metadata]
creation_date = "2025/06/30"
integration = ["endpoint", "system", "windows", "auditd_manager", "m365_defender", "crowdstrike"]
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s1 maybe? cc @w0rk3r

w0rk3r
w0rk3r reviewed Jun 30, 2025
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rules/cross-platform/defense_evasion_whitespace_padding_command_line.toml
type = "esql"

query = '''
FROM logs-* metadata _id, _version, _index
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We may want to limit the indexes here, logs-* would probably be expensive as it will search for all integrations

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if the integration is not enabled it may error with Unknown Index, listing all the integration indexes may result also in perf hit.

@zez3
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zez3 commented Jul 1, 2025

This supersedes the old deprecated rule #2315

@tradebot-elastic
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tradebot-elastic commented Aug 18, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Command Line Obfuscation via Whitespace Padding (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Aug 18, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Command Line Obfuscation via Whitespace Padding (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Aug 18, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Command Line Obfuscation via Whitespace Padding (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Aug 18, 2025 •
edited
Loading

⛔️ Test failed

Results
  • ❌ Command Line Obfuscation via Whitespace Padding (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Aug 18, 2025 •
edited
Loading

⛔️ Test failed

Results
  • ❌ Command Line Obfuscation via Whitespace Padding (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@Samirbous Samirbous merged commit 1557eae into main Aug 18, 2025
12 checks passed
@Samirbous Samirbous deleted the Samirbous-patch-1 branch August 18, 2025 14:26
terrancedejesus
terrancedejesus reviewed Aug 18, 2025
View reviewed changes
rules/cross-platform/defense_evasion_whitespace_padding_command_line.toml
FROM logs-* metadata _id, _version, _index
| where event.category == "process" and event.type == "start" and event.action != "fork"
// more than 100 spaces in process.command_line
| eval multi_spaces = LOCATE(process.command_line, space(100))
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Sorry I missed this, should have been Esql.process_command_line_locate or Esql.process_command_line_white_spaces. This field will not get picked up in telemetry as multi_spaces.

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we don't need it in telem 👍

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Reviewers

@w0rk3r w0rk3r w0rk3r left review comments

@Aegrah Aegrah Aegrah approved these changes

@terrancedejesus terrancedejesus terrancedejesus approved these changes

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@Samirbous Samirbous

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backport: auto Domain: Endpoint OS: Windows windows related rules Rule: New Proposal for new rule

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6 participants

@Samirbous @tradebot-elastic @zez3 @w0rk3r @Aegrah @terrancedejesus