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YARA · Avast / Gen Digital IOC

AVASTTI_Cobaltstrike_Beacon_Xored_X86

No description has been set in the source file - AvastTI

Hack toolCobalt StrikeAvast / Gen Digital IOCDetection Rule License 1.1Compiles with YARA-X
Author
Gen Threat Labs
Date
2021-07-08
Modified
2026-03-11
Score / Quality
75 / 90

What this rule detects

No description has been set in the source file - AvastTI

Associated malware family: Cobalt Strike.

It defines 3 patterns (0 text, 3 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
cobaltstrike-beacon-xored-x86.yarDetection Rule License 1.1
rule AVASTTI_Cobaltstrike_Beacon_Xored_X86
{
	meta:
		description = "No description has been set in the source file - AvastTI"
		author = "Gen Threat Labs"
		id = "d93c20e6-3e01-5132-88a0-63ace507cae9"
		date = "2021-07-08"
		modified = "2026-03-11"
		reference = "https://github.com/gendigitalinc/ioc"
		source_url = "https://github.com/avast/ioc/blob/a450ddabed95984422909c75ac52b6841f685983/CobaltStrike/yara_rules/cs_rules.yar#L705-L726"
		license_url = "N/A"
		logic_hash = "1415c8ab5b4ddd6eb0f561b570358f04f967621dfc6274e0380879563b612c27"
		score = 75
		quality = 90
		tags = ""

	strings:
		$h01 = { FC E8??000000 [0-32] EB27 ?? 8B?? 83??04 8B?? 31?? 83??04 ?? 8B?? 31?? 89?? 31?? 83??04 83??04 31?? 39?? 7402 EBEA ?? FF?? E8D4FFFFFF }
		$h02 = { FC E8??000000 [0-32] EB2B ?? 8B??00 83C504 8B??00 31?? 83C504 55 8B??00 31?? 89??00 31?? 83C504 83??04 31?? 39?? 7402 EBE8 ?? FF?? E8D0FFFFFF }
		$h11 = { 7402 EB(E8|EA) ?? FF?? E8(D0|D4)FFFFFF }

	condition:
		any of ( $h0* ) and ( uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x4D5AE800 or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x904D5AE8 or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x90904D5A or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x9090904D or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x90909090 )
}

Strings (3 patterns)

IdentifierTypeValueModifiers
$h01hex{ FC E8??000000 [0-32] EB27 ?? 8B?? 83??04 8B?? 31?? 83??04 ?? 8B?? 31?? 89?? 31?? 83??04 83??04 31?? 39?? 7402 EBEA ?? FF?? E8D4FFFFFF }
$h02hex{ FC E8??000000 [0-32] EB2B ?? 8B??00 83C504 8B??00 31?? 83C504 55 8B??00 31?? 89??00 31?? 83C504 83??04 31?? 39?? 7402 EBE8 ?? FF?? E8D0FFFFFF }
$h11hex{ 7402 EB(E8|EA) ?? FF?? E8(D0|D4)FFFFFF }

Condition

any of ( $h0* ) and ( uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x4D5AE800 or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x904D5AE8 or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x90904D5A or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x9090904D or uint32be( @h11 + 12 ) ^ uint32be( @h11 + 20 ) == 0x90909090 )

In plain words (Heuristic)

  • At least one pattern in ( $h0* ) must match.

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References

Licence & attribution

Author: Gen Threat Labs

Source repository: Avast / Gen Digital IOC @ a450ddabed

Licence: Detection Rule License 1.1 (repository licence)

Original rule

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

Rule id: d93c20e6-3e01-5132-88a0-63ace507cae9

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