YARA · SEKOIA.IO Community

SEKOIA_Rule_Lazarus_Generic_Downloader_7C3F94702Fa7

Detects a Generic Downloader used by Lazarus

APT / threat actorSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X

Author: Sekoia.io
Date: 2022-08-08
Modified: 2024-12-19
Score / Quality: 75 / 80

What this rule detects

Detects a Generic Downloader used by Lazarus

Targets: Windows PE.

It defines 5 patterns (5 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

rule-lazarus-generic-downloader-7c3f94702fa7.yarDetection Rule License 1.1

rule SEKOIA_Rule_Lazarus_Generic_Downloader_7C3F94702Fa7 : FILE
{
	meta:
		description = "Detects a Generic Downloader used by Lazarus"
		author = "Sekoia.io"
		id = "eb0f0a91-5e72-4358-91a3-7c3f94702fa7"
		date = "2022-08-08"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/rule_lazarus_generic_downloader_7c3f94702fa7.yar#L1-L21"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "1ee58eb760fb74ef089f7d3eb423f314fe1c22e8c85b01eba0e965dea8c846ce"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$ = "%s%s%s%s = %s%s%s%s"
		$ = "sec-ch-ua-mobile: ?0"
		$ = "%s>%s"
		$ = "d$f92&^$#FESAfaSDage#FDa"
		$ = "Sec-Fetch-User: ?1"

	condition:
		uint16be( 0 ) == 0x4d5a and filesize < 200KB and 3 of them
}

Strings (5 patterns)

Identifier	Type	Value
$	text	"%s%s%s%s = %s%s%s%s"
$	text	"sec-ch-ua-mobile: ?0"
$	text	"%s>%s"
$	text	"d$f92&^$#FESAfaSDage#FDa"
$	text	"Sec-Fetch-User: ?1"

Condition

uint16be( 0 ) == 0x4d5a and filesize < 200KB and 3 of them

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
The file must be smaller than 200KB (a cheap guard that skips large files).
At least 3 patterns in the rule must match.

Test this rule in your browser

Drop a file to scan it with this rule using YARA-X compiled to WebAssembly. Nothing is uploaded.

Drop a file here or click to chooseScanned locally with YARA-X. Files up to 200 MB.

Open in editor

References

https://github.com/SEKOIA-IO/Community

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: eb0f0a91-5e72-4358-91a3-7c3f94702fa7

Metadata

version	1.0
classification	TLP:CLEAR

Tags:FILE

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