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Detect a dropper used to deploy an implant via side loading. This dropper has specifically been observed deploying REDLE

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: 2026-05-18T23:00:00Z · Confidence: medium

Hunt Hypothesis

A dropper is being used to deploy the REDLEAVES and PlugX implants via side loading, indicating potential lateral movement and persistence in the network. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage malware deployment attempts before they establish deeper network access.

YARA Rule

rule Dropper_DeploysMalwareViaSideLoading {
meta:
        description = "Detect a dropper used to deploy an implant via side loading. This dropper has specifically been observed deploying REDLEAVES & PlugX"
        author = "USG"
        true_positive = "5262cb9791df50fafcb2fbd5f93226050b51efe400c2924eecba97b7ce437481: drops REDLEAVES. 6392e0701a77ea25354b1f40f5b867a35c0142abde785a66b83c9c8d2c14c0c3: drops plugx. "
        reference = "https://www.us-cert.gov/ncas/alerts/TA17-117A"

strings:
        $UniqueString = {2e 6c 6e 6b [0-14] 61 76 70 75 69 2e 65 78 65} // ".lnk" near "avpui.exe"
        $PsuedoRandomStringGenerator = {b9 1a [0-6] f7 f9 46 80 c2 41 88 54 35 8b 83 fe 64} // Unique function that generates a 100 character pseudo random string.

condition:
        any of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 2 string patterns in its detection logic.

References

False Positive Guidance

Original source: https://github.com/Yara-Rules/rules/blob/main/malware/APT_APT10.yar