YARA · SEKOIA.IO Community

SEKOIA_Apt_Boldmove_Strings

Detects BOLDMOVE via strings

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

Author: Sekoia.io
Date: 2023-01-16
Modified: 2024-12-19
Score / Quality: 75 / 80

What this rule detects

Detects BOLDMOVE via strings

Associated malware family: Boldmove.

Targets: Windows PE, Linux ELF.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-boldmove-strings.yarDetection Rule License 1.1

rule SEKOIA_Apt_Boldmove_Strings : FILE
{
	meta:
		description = "Detects BOLDMOVE via strings"
		author = "Sekoia.io"
		id = "0458e282-f92f-4600-964a-de6b66b4a82d"
		date = "2023-01-16"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/apt_boldmove_strings.yar#L1-L20"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "71649451b88629da1779c0856b2f1f60f87501962c69556f7943b049688a2d96"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$s1 = "cwd=%s" ascii wide
		$s2 = "executable=%s" ascii wide
		$s3 = "curl/6.12.34" ascii wide
		$s4 = "www.example.com" ascii wide
		$s5 = "GET /ws HTTP/1.1" ascii wide

	condition:
		( uint32be( 0 ) == 0x7f454c46 or uint16be( 0 ) == 0x4d5a ) and filesize < 4MB and 4 of them
}

Strings (5 patterns)

Identifier	Type	Value	Modifiers
$s1	text	"cwd=%s"	ascii wide
$s2	text	"executable=%s"	ascii wide
$s3	text	"curl/6.12.34"	ascii wide
$s4	text	"www.example.com"	ascii wide
$s5	text	"GET /ws HTTP/1.1"	ascii wide

Condition

( uint32be( 0 ) == 0x7f454c46 or uint16be( 0 ) == 0x4d5a ) and filesize < 4MB and 4 of them

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
The file must start with the ELF header — a Linux/Unix executable.
The file must be smaller than 4MB (a cheap guard that skips large files).
At least 4 patterns in the rule must match.

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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: 0458e282-f92f-4600-964a-de6b66b4a82d

Metadata

version	1.0
classification	TLP:CLEAR

Tags:FILE

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