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YARA · SEKOIA.IO Community

SEKOIA_Guloader_Unpacker_Decoded

GuLoader Unpacker b64 decoded

Suspicious / huntingSEKOIA.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

GuLoader Unpacker b64 decoded

It defines 4 patterns (3 text, 1 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

guloader-unpacker-decoded.yarDetection Rule License 1.1
rule SEKOIA_Guloader_Unpacker_Decoded : FILE
{
	meta:
		description = "GuLoader Unpacker b64 decoded"
		author = "Sekoia.io"
		id = "ca3f4fce-b3a1-4672-a2ca-29ea347eb23d"
		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_unpacker_decoded.yar#L1-L18"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "5de4a147b2dea8a144905b7f1786199bfeef3006ac58179409cfd3dcaa116725"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$jumps = {71 01 9b 71 01 9b}
		$s1 = "([String]$"
		$s2 = "For($"
		$s3 = ",[Parameter(Position = 1)] [Type] $"

	condition:
		filesize < 500KB and @jumps < 1000 and 2 of ( $s* )
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$jumpshex{71 01 9b 71 01 9b}
$s1text"([String]$"
$s2text"For($"
$s3text",[Parameter(Position = 1)] [Type] $"

Condition

filesize < 500KB and @jumps < 1000 and 2 of ( $s* )

In plain words (Heuristic)

  • The file must be smaller than 500KB (a cheap guard that skips large files).
  • At least 2 patterns in ( $s* ) must match.

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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: ca3f4fce-b3a1-4672-a2ca-29ea347eb23d

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE