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Look for Blowfish constants

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: 2026-04-23T09:00:00Z · Confidence: medium

Hunt Hypothesis

The detection rule identifies potential adversary activity by searching for Blowfish constants, which may indicate the use of cryptographic routines associated with data encryption or exfiltration. SOC teams should proactively hunt for this behavior in Azure Sentinel to uncover early-stage malware or data manipulation attempts that leverage cryptographic techniques.

YARA Rule

rule BLOWFISH_Constants {
	meta:
		author = "phoul (@phoul)"
		description = "Look for Blowfish constants"
		date = "2014-01"
		version = "0.1"
	strings:
		$c0 = { D1310BA6 }
		$c1 = { A60B31D1 }	
		$c2 = { 98DFB5AC }
		$c3 = { ACB5DF98 }
		$c4 = { 2FFD72DB }
		$c5 = { DB72FD2F }
		$c6 = { D01ADFB7 }
		$c7 = { B7DF1AD0 }
		$c8 = { 4B7A70E9 }
		$c9 = { E9707A4B }
		$c10 = { F64C261C }
		$c11 = { 1C264CF6 }
	condition:
		6 of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 12 string patterns in its detection logic.

False Positive Guidance

Original source: https://github.com/Yara-Rules/rules/blob/main/crypto/crypto_signatures.yar