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SEKOIA_Guloader_Vbscript

visual basic script 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

visual basic script delivering GuLoader

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

Summary generated from the rule's metadata and condition.

Rule source

guloader-vbscript.yarDetection Rule License 1.1
rule SEKOIA_Guloader_Vbscript : FILE
{
	meta:
		description = "visual basic script delivering GuLoader"
		author = "Sekoia.io"
		id = "3472e403-b1e6-4fdf-9770-af42d505b556"
		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_vbscript.yar#L1-L17"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "d0398b19ec57cff8afd52b06dc9da18788b1eefdf6be70650138e9b342d91d24"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$s1 = " = CreateObject(\"WScript.Shell\")"
		$s2 = " = Join("
		$s3 = ",vbnullstring)"

	condition:
		filesize < 20KB and all of them and #s1 > 1 and @s3- @s2 < 16
}

Strings (3 patterns)

IdentifierTypeValueModifiers
$s1text" = CreateObject(\"WScript.Shell\")"
$s2text" = Join("
$s3text",vbnullstring)"

Condition

filesize < 20KB and all of them and #s1 > 1 and @s3- @s2 < 16

In plain words (Heuristic)

  • The file must be smaller than 20KB (a cheap guard that skips large files).
  • All patterns in the rule must match.
  • Pattern $s1 must occur > 1 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: 3472e403-b1e6-4fdf-9770-af42d505b556

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE