Sigma rule: .Class Extension URI Ending Request

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-5e2d31e05dff, updated 2024-02-26T00:00:00.000Z.

Rule

Title
.Class Extension URI Ending Request
Status
test
Level
medium
Author
Andreas Hunkeler (@Karneades)
Date
2021-12-21
Modified
2024-02-26
File
rules-threat-hunting/web/proxy_generic/proxy_susp_class_extension_request.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects requests to URI ending with the ".class" extension in proxy logs.
This could rules can be used to hunt for potential downloads of Java classes as seen for example in Log4shell exploitation attacks against Log4j.

Log source

category
proxy

Detection

selection:
    c-uri|endswith: '.class'
condition: selection

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.initial-access
  • detection.threat-hunting

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-threat-hunting/web/proxy_generic/proxy_susp_class_extension_request.yml

Sources and licences

  • SigmaHQ

    ".Class Extension URI Ending Request" by Andreas Hunkeler (@Karneades) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-threat-hunting/web/proxy_generic/proxy_susp_class_extension_request.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: .Class Extension URI Ending Request",
entity page, dataset version ref-5e2d31e05dff, updated 2024-02-26T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/53c15703-b04c-42bb-9055-1937ddfb3392 (accessed 2026-11-03).
Underlying source: SigmaHQ rule 53c15703-b04c-42bb-9055-1937ddfb3392, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.