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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_CN_Wocao_Xserver_Powershell_B64Encoded

Piece of Base64 encoded data from the XServer PowerShell dropper

APT / threat actorSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Fox-IT SRT
Date
2019-12-20
Modified
2023-12-05
Score / Quality
75 / 85

What this rule detects

Piece of Base64 encoded data from the XServer PowerShell dropper

It defines 2 patterns (2 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
apt-mal-cn-wocao-xserver-powershell-b64encoded.yarDetection Rule License 1.1
rule SIGNATURE_BASE_APT_MAL_CN_Wocao_Xserver_Powershell_B64Encoded
{
	meta:
		description = "Piece of Base64 encoded data from the XServer PowerShell dropper"
		author = "Fox-IT SRT"
		id = "01e38cfb-b245-5398-b037-6d1d2fb726ee"
		date = "2019-12-20"
		modified = "2023-12-05"
		reference = "https://www.fox-it.com/en/news/whitepapers/operation-wocao-shining-a-light-on-one-of-chinas-hidden-hacking-groups/"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_op_wocao.yar#L143-L155"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "77315f0fc8387fa87892fc8fcea1f6e8a95560049aaa9a87519859020d0a7a3e"
		score = 75
		quality = 85
		tags = ""

	strings:
		$header_47000 = "5T39c9u2kr/nr2A0Ny2VKIzkfLRJntuJHafPN/nwWG777rUZDy3BNq8UqSEpx26b"
		$header_25667 = "5T1rc9u2st/zKxjNmZZKFEZyErdJ6nZsx+nxnTjxWGp77mkzHlqCbd5SpIak/Gjr"

	condition:
		any of them
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$header_47000text"5T39c9u2kr/nr2A0Ny2VKIzkfLRJntuJHafPN/nwWG777rUZDy3BNq8UqSEpx26b"
$header_25667text"5T1rc9u2st/zKxjNmZZKFEZyErdJ6nZsx+nxnTjxWGp77mkzHlqCbd5SpIak/Gjr"

Condition

any of them

In plain words (Heuristic)

  • At least one pattern in the rule must match.

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References

Licence & attribution

Author: Fox-IT SRT

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

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: 01e38cfb-b245-5398-b037-6d1d2fb726ee

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