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rar with js

yara LOW Yara-Rules
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This rule was pulled from an open-source repository and enriched with AI. Validate in a test environment before deploying to production.
View original rule at Yara-Rules →
Retrieved: 2026-06-29T11:00:01Z · Confidence: medium

Hunt Hypothesis

This hypothesis posits that adversaries are embedding JavaScript files within RAR archives to execute malicious payloads while evading standard static analysis of common container formats. Proactive hunting for this pattern in Azure Sentinel is critical to identify early-stage supply chain compromises or phishing campaigns that leverage the low-severity nature of RAR containers to bypass initial alert thresholds.

YARA Rule

rule rar_with_js
{
  strings:
  $h1 = "Rar!" 
  $s1 = ".js" nocase
    
  condition:
    $h1 at 0 and $s1
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 2 string patterns in its detection logic.

False Positive Guidance

Here are 4 specific false positive scenarios for the rar_with_js detection rule in an enterprise environment, along with suggested filters or exclusions:

Original source: https://github.com/Yara-Rules/rules/blob/main/malware/MALW_Rockloader.yar