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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_CN_Wocao_Xserver_Powershell_Dropper

Strings from the PowerShell dropper of XServer

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

Strings from the PowerShell dropper of XServer

It defines 1 patterns (1 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
apt-mal-cn-wocao-xserver-powershell-dropper.yarDetection Rule License 1.1
rule SIGNATURE_BASE_APT_MAL_CN_Wocao_Xserver_Powershell_Dropper
{
	meta:
		description = "Strings from the PowerShell dropper of XServer"
		author = "Fox-IT SRT"
		id = "97169ab4-d68d-5137-83de-d9cac975747e"
		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#L157-L168"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "640c9e52f3cf3df4e954177624e6fba4bab80a2c9442b718fe90e8577dafbbd6"
		score = 75
		quality = 85
		tags = ""

	strings:
		$encfile = "New-Object IO.Compression.DeflateStream([IO.MemoryStream][Convert]::FromBase64String($encfile)"

	condition:
		all of them
}

Strings (1 patterns)

IdentifierTypeValueModifiers
$encfiletext"New-Object IO.Compression.DeflateStream([IO.MemoryStream][Convert]::FromBase64String($encfile)"

Condition

all of them

In plain words (Heuristic)

  • All patterns 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: 97169ab4-d68d-5137-83de-d9cac975747e

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