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SEKOIA_Loader_Win_Jennlog

Jennlog loader used to deliver the Apostle ransomware

MalwareJennlogSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X (with warnings)
Author
Sekoia.io
Date
2021-10-04
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Jennlog loader used to deliver the Apostle ransomware

Associated malware family: Jennlog.

Targets: Windows PE.

It has no patterns: the condition alone decides (modules, file properties or other rules). YARA modules used: pe, hash.

YARA-X says: warning[deprecated_field]: field `number_of_sections` is deprecated

Summary generated from the rule's metadata and condition.

Rule source

Includes the imports needed to compile it on its own.

loader-win-jennlog.yarDetection Rule License 1.1
import "pe"
import "hash"

rule SEKOIA_Loader_Win_Jennlog
{
	meta:
		description = "Jennlog loader used to deliver the Apostle ransomware"
		author = "Sekoia.io"
		id = "a69088e5-207f-494f-876b-766b8050e8c2"
		date = "2021-10-04"
		modified = "2024-12-19"
		reference = "https://www.sentinelone.com/labs/new-version-of-apostle-ransomware-reemerges-in-targeted-attack-on-higher-education/"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/loader_win_jennlog.yar#L4-L24"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "0ffcd1f35570b28a1bd6f9a0361f8f921942f7345dcb2896fc092bb92f7d4d6d"
		score = 75
		quality = 80
		tags = ""
		version = "1.0"
		classification = "TLP:CLEAR"

	condition:
		pe.timestamp== 3140259112 or for any i in ( 0 .. pe.number_of_sections -1 ) : ( hash.md5 ( pe.sections [ i ] . raw_data_offset , pe.sections [ i ] . raw_data_size ) == "4c4577276ff0323d9aedcc39ecf2c964" ) or for any i in ( 0 .. pe.number_of_resources -1 ) : ( hash.sha256 ( pe.resources [ i ] . offset , pe.resources [ i ] . length ) == "8476a7fca587f1e5d3ae076293b9fbcccbebc4bd4f7b783228ad5da39305a3d9" )
}

Condition

pe.timestamp== 3140259112 or for any i in ( 0 .. pe.number_of_sections -1 ) : ( hash.md5 ( pe.sections [ i ] . raw_data_offset , pe.sections [ i ] . raw_data_size ) == "4c4577276ff0323d9aedcc39ecf2c964" ) or for any i in ( 0 .. pe.number_of_resources -1 ) : ( hash.sha256 ( pe.resources [ i ] . offset , pe.resources [ i ] . length ) == "8476a7fca587f1e5d3ae076293b9fbcccbebc4bd4f7b783228ad5da39305a3d9" )

In plain words (Heuristic)

  • A for-loop checks a property over several matches or items.
  • Uses the pe module.
  • Uses the hash module.
  • Compares a hash of the file or a part of it.
  • Checks PE sections (names, count or properties).

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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: a69088e5-207f-494f-876b-766b8050e8c2

Metadata

version1.0
classificationTLP:CLEAR