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YARA · SEKOIA.IO Community

SEKOIA_Guloader_Powershell_1

Powershell downloading decoy and delivering GuLoader

GenericSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X
Author
Sekoia.io
Date
2024-02-07
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Powershell downloading decoy and delivering GuLoader

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

Summary generated from the rule's metadata and condition.

Rule source

guloader-powershell-1.yarDetection Rule License 1.1
rule SEKOIA_Guloader_Powershell_1 : FILE
{
	meta:
		description = "Powershell downloading decoy and delivering GuLoader"
		author = "Sekoia.io"
		id = "28c68991-db8b-4f00-b3a3-17286418a4ed"
		date = "2024-02-07"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/guloader_powershell_1.yar#L1-L18"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "9fd2d0e31f939e7e96444eaa4802c9c33407c5fb77067670d8ce2d3796199961"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$s1 = "powershell -win hidden"
		$s2 = "=iex($"
		$s3 = ".Replace('"
		$s4 = "$(Get-ChildItem -Include *.lnk -Name));"

	condition:
		all of them and filesize < 10KB and #s3 > 3
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$s1text"powershell -win hidden"
$s2text"=iex($"
$s3text".Replace('"
$s4text"$(Get-ChildItem -Include *.lnk -Name));"

Condition

all of them and filesize < 10KB and #s3 > 3

In plain words (Heuristic)

  • The file must be smaller than 10KB (a cheap guard that skips large files).
  • All patterns in the rule must match.
  • Pattern $s3 must occur > 3 times.

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References

Licence & attribution

Author: Sekoia.io

Source repository: SEKOIA.IO Community @ a438a5901a

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: 28c68991-db8b-4f00-b3a3-17286418a4ed

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE