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WITHSECURELABS_GREYVIBE_JSLOADER_2

Detects common strings found across one of GREYVIBE's loaders (observed in PhantomMail campaign)

GenericWithSecure Labs IOCsBSD 2-Clause LicenseCompiles with YARA-X
Author
WithSecure
Date
2026-05-28
Score / Quality
75 / 75

What this rule detects

Detects common strings found across one of GREYVIBE's loaders (observed in PhantomMail campaign)

It defines 4 patterns (4 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

greyvibe-jsloader-2.yarBSD 2-Clause License
rule WITHSECURELABS_GREYVIBE_JSLOADER_2
{
	meta:
		description = "Detects common strings found across one of GREYVIBE's loaders (observed in PhantomMail campaign)"
		author = "WithSecure"
		id = "9901d2df-6539-51c6-a24d-c06a7e898a6a"
		date = "2026-05-28"
		modified = "2026-05-28"
		reference = "https://github.com/WithSecureLabs/iocs"
		source_url = "https://github.com/WithSecureLabs/iocs/blob/1a8384468dd292c6d2c5114c32e42dc0da1f5ae1/GREYVIBE/greyvibe.yara#L61-L73"
		license_url = "https://github.com/WithSecureLabs/iocs/blob/1a8384468dd292c6d2c5114c32e42dc0da1f5ae1/LICENSE"
		logic_hash = "c6fc0969bb62de731e9770447df565e427b03c69851708a0a30a4da20f176236"
		score = 75
		quality = 75
		tags = ""

	strings:
		$a = "// String Reconstruction"
		$b = "Math.cos"
		$c = "Math.sin"
		$d = ".join(\"\")"

	condition:
		all of them
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$atext"// String Reconstruction"
$btext"Math.cos"
$ctext"Math.sin"
$dtext".join(\"\")"

Condition

all of them

In plain words (Heuristic)

  • All patterns in the rule must match.

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References

Licence & attribution

Author: WithSecure

Source repository: WithSecure Labs IOCs @ 1a8384468d

Licence: BSD 2-Clause License (repository licence)

Copyright notice: Copyright (c) 2022, WithSecure Oyj

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: 9901d2df-6539-51c6-a24d-c06a7e898a6a