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Detetcs a certain Nanocore RAT sample

yara HIGH Yara-Rules
backdoorcommunity
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: 2026-07-13T11:00:00Z · Confidence: medium

Hunt Hypothesis

This hunt targets adversaries deploying the specific Nanocore Remote Access Trojan (RAT) to establish persistent command-and-control channels and exfiltrate sensitive data from Azure workloads. Proactively hunting for this signature in Azure Sentinel is critical because early identification of this high-severity threat allows the SOC team to isolate compromised endpoints before lateral movement or data theft occurs.

YARA Rule

rule Nanocore_RAT_Sample_2 {
	meta:
		description = "Detetcs a certain Nanocore RAT sample"
		author = "Florian Roth"
		score = 75
		reference = "https://www.sentinelone.com/blogs/teaching-an-old-rat-new-tricks/"
		date = "2016-04-22"
		hash1 = "51142d1fb6c080b3b754a92e8f5826295f5da316ec72b480967cbd68432cede1"
	strings:
		$s1 = "U4tSOtmpM" fullword ascii
		$s2 = ")U71UDAU_QU_YU_aU_iU_qU_yU_" fullword wide
		$s3 = "Cy4tOtTmpMtTHVFOrR" fullword ascii
	condition:
		uint16(0) == 0x5a4d and filesize < 40KB and all of ($s*)
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 3 string patterns in its detection logic.

References

False Positive Guidance

Here are 5 specific false positive scenarios for the Nanocore RAT detection rule in an enterprise environment, along with targeted filtering strategies:

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