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VOLEXITY_Apt_Win_Powerstar

Custom PowerShell backdoor used by Charming Kitten.

APT / threat actorVolexity threat-intelBSD 2-Clause LicenseCompiles with YARA-X
Author
threatintel@volexity.com
Date
2021-10-13
Modified
2023-09-20
Score / Quality
75 / 80

What this rule detects

Custom PowerShell backdoor used by Charming Kitten.

It defines 8 patterns (8 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

apt-win-powerstar.yarBSD 2-Clause License
rule VOLEXITY_Apt_Win_Powerstar : CHARMINGKITTEN
{
	meta:
		description = "Custom PowerShell backdoor used by Charming Kitten."
		author = "threatintel@volexity.com"
		id = "febcd23b-6545-571b-905d-18dffe8e913f"
		date = "2021-10-13"
		modified = "2023-09-20"
		reference = "https://github.com/volexity/threat-intel"
		source_url = "https://github.com/volexity/threat-intel/blob/3a9d0b52459877ee866a9a0ba06e60059b778c77/2023/2023-06-28 POWERSTAR/indicators/rules.yar#L122-L150"
		license_url = "https://github.com/volexity/threat-intel/blob/3a9d0b52459877ee866a9a0ba06e60059b778c77/LICENSE.txt"
		hash = "de99c4fa14d99af791826a170b57a70b8265fee61c6b6278d3fe0aad98e85460"
		logic_hash = "2cbf59eaee60a8f84b1ac35cec3b01592a2a0f56c92a2db218bb26a15be24bf3"
		score = 75
		quality = 80
		tags = "CHARMINGKITTEN"
		memory_suitable = 1
		license = "See license at https://github.com/volexity/threat-intel/blob/main/LICENSE.txt"

	strings:
		$appname = "[AppProject.Program]::Main()" ascii wide
		$langfilters1 = "*shar*" ascii wide
		$langfilters2 = "*owers*" ascii wide
		$definitions1 = "[string]$language" ascii wide
		$definitions2 = "[string]$Command" ascii wide
		$definitions3 = "[string]$ThreadName" ascii wide
		$definitions4 = "[string]$StartStop" ascii wide
		$sess = "$session = $v + \";;\" + $env:COMPUTERNAME + $mac;" ascii wide

	condition:
		$appname or all of ( $langfilters* ) or all of ( $definitions* ) or $sess
}

Strings (8 patterns)

IdentifierTypeValueModifiers
$appnametext"[AppProject.Program]::Main()"ascii wide
$langfilters1text"*shar*"ascii wide
$langfilters2text"*owers*"ascii wide
$definitions1text"[string]$language"ascii wide
$definitions2text"[string]$Command"ascii wide
$definitions3text"[string]$ThreadName"ascii wide
$definitions4text"[string]$StartStop"ascii wide
$sesstext"$session = $v + \";;\" + $env:COMPUTERNAME + $mac;"ascii wide

Condition

$appname or all of ( $langfilters* ) or all of ( $definitions* ) or $sess

In plain words (Heuristic)

  • All patterns in ( $langfilters* ) must match.
  • All patterns in ( $definitions* ) must match.
  • Pattern $appname must be present.
  • Pattern $sess must be present.

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References

Sample hashes

Hashes of samples the author lists in the rule's meta (look them up in your threat-intelligence platform).

  • de99c4fa14d99af791826a170b57a70b8265fee61c6b6278d3fe0aad98e85460

Licence & attribution

Author: threatintel@volexity.com

Source repository: Volexity threat-intel @ 3a9d0b5245

Licence: BSD 2-Clause License (stated in the rule's own meta)

“See license at https://github.com/volexity/threat-intel/blob/main/LICENSE.txt”

Copyright notice: Copyright 2022 by Volexity, Inc.

Original rule

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

Rule id: febcd23b-6545-571b-905d-18dffe8e913f

Metadata

memory_suitable1

Tags:CHARMINGKITTEN