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[New Rule] Web Server Unusual Spike in Error Logs #5339

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Merged
merged 13 commits into from
Nov 24, 2025
Merged

[New Rule] Web Server Unusual Spike in Error Logs #5339

merged 13 commits into from
Nov 24, 2025

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@Aegrah
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@Aegrah Aegrah commented Nov 19, 2025

Summary

This rule detects unusual spikes in error logs from web servers, which may indicate reconnaissance activities such as vulnerability scanning or fuzzing attempts by adversaries. These activities often generate a high volume of error responses as they probe for weaknesses in web applications. Error response codes may potentially indicate server-side issues that could be exploited.

@Aegrah Aegrah self-assigned this Nov 19, 2025
@Aegrah Aegrah added Rule: New Proposal for new rule Team: TRADE labels Nov 19, 2025
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github-actions bot commented Nov 19, 2025

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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tradebot-elastic commented Nov 19, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Unusual Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 19, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Unusual Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 21, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Unusual Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

w0rk3r
w0rk3r reviewed Nov 23, 2025
View reviewed changes
rules/cross-platform/reconnaissance_web_server_unusual_spike_in_error_logs.toml Outdated
by source.ip
| where
Esql.event_count > 25
| limit 100
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@w0rk3r w0rk3r Nov 23, 2025

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How does this behave in ES|QL rules?

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@terrancedejesus terrancedejesus Nov 24, 2025

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Limits results to 100 only which is then how many alerts would be generated, if I recall

w0rk3r
w0rk3r reviewed Nov 23, 2025
View reviewed changes
rules/cross-platform/reconnaissance_web_server_unusual_spike_in_error_logs.toml Outdated
interval = "1h"
language = "esql"
license = "Elastic License v2"
name = "Web Server Unusual Spike in Error Logs"
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@w0rk3r w0rk3r Nov 23, 2025

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How are we checking if this is unusual activity? Or if this is a spike?

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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Unusual Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@Aegrah
Remove event limit from error log rule
a3ea367 
Removed limit on the number of events in the rule.
@tradebot-elastic
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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Unusual Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@w0rk3r w0rk3r mentioned this pull request Nov 24, 2025
Merged
Samirbous
Samirbous reviewed Nov 24, 2025
View reviewed changes
rules/cross-platform/reconnaissance_web_server_unusual_spike_in_error_logs.toml Outdated
timestamp_override = "event.ingested"
type = "esql"
query = '''
from
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@Samirbous Samirbous Nov 24, 2025

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maybe u need to add where source.ip != null to avoid matches on error logs with empty source.ip

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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Potential Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Potential Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Web Server Potential Spike in Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@eric-forte-elastic
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eric-forte-elastic commented Nov 24, 2025

ES|QL multi line index support from #5356 will address index error.

terrancedejesus and others added 2 commits November 24, 2025 13:04
@terrancedejesus @w0rk3r
Update rules/cross-platform/reconnaissance_web_server_unusual_spike_i…
8d8bebf 
…n_error_logs.toml

Co-authored-by: Jonhnathan <26856693+w0rk3r@users.noreply.github.com>
@terrancedejesus @shashank-elastic
Update rules/cross-platform/reconnaissance_web_server_unusual_spike_i…
828dfa5 
…n_error_logs.toml

Co-authored-by: shashank-elastic <91139415+shashank-elastic@users.noreply.github.com>
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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Potential Spike in Web Server Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Potential Spike in Web Server Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Potential Spike in Web Server Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 24, 2025 •
edited
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⛔️ Test failed

Results
  • ❌ Potential Spike in Web Server Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@tradebot-elastic
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tradebot-elastic commented Nov 24, 2025 •
edited
Loading

⛔️ Test failed

Results
  • ❌ Potential Spike in Web Server Error Logs (esql)
    • coverage_issue: no_rta
    • stack_validation_failed: no_rta

@terrancedejesus terrancedejesus merged commit 4f8c967 into main Nov 24, 2025
13 checks passed
@terrancedejesus terrancedejesus deleted the new-rule-spike-error-logs branch November 24, 2025 18:18
@eric-forte-elastic eric-forte-elastic mentioned this pull request Nov 24, 2025
Merged
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@w0rk3r w0rk3r w0rk3r left review comments

@shashank-elastic shashank-elastic shashank-elastic left review comments

@terrancedejesus terrancedejesus terrancedejesus approved these changes

@Samirbous Samirbous Samirbous approved these changes

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@Aegrah Aegrah

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@Aegrah @tradebot-elastic @eric-forte-elastic @w0rk3r @Samirbous @shashank-elastic @terrancedejesus