YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_LUA_Hunting_Lua_SKIPJACK_2

Hunting rule looking for strings observed in SKIPJACK samples.

APT / threat actorSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X

Author: Mandiant
Date: 2023-06-15
Modified: 2023-12-05
Score / Quality: 70 / 85

What this rule detects

Hunting rule looking for strings observed in SKIPJACK samples.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-mal-lua-hunting-lua-skipjack-2.yarDetection Rule License 1.1

rule SIGNATURE_BASE_APT_MAL_LUA_Hunting_Lua_SKIPJACK_2
{
	meta:
		description = "Hunting rule looking for strings observed in SKIPJACK samples."
		author = "Mandiant"
		id = "e1eac294-fe60-5bb2-bae4-0f7bcbe6b1db"
		date = "2023-06-15"
		modified = "2023-12-05"
		reference = "https://www.mandiant.com/resources/blog/barracuda-esg-exploited-globally"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_barracuda_esg_unc4841_jun23.yar#L195-L212"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "87847445f9524671022d70f2a812728f"
		logic_hash = "093e8857c410bd30a076f87ef63d7e1e66f50e3dce75b4add67161782386ee24"
		score = 70
		quality = 85
		tags = ""

	strings:
		$str1 = "hdr:name() == 'Content-ID'"
		$str2 = "hdr:body() ~= nil"
		$str3 = "string.match(hdr:body(),\"^[%w%+/=\\r\\n]+$\")"
		$str4 = "openssl aes-256-cbc"
		$str5 = "| base64 -d| sh 2>"

	condition:
		all of them
}

Strings (5 patterns)

Identifier	Type	Value
$str1	text	"hdr:name() == 'Content-ID'"
$str2	text	"hdr:body() ~= nil"
$str3	text	"string.match(hdr:body(),\"^[%w%+/=\\r\\n]+$\")"
$str4	text	"openssl aes-256-cbc"
$str5	text	"\| base64 -d\| sh 2>"

Condition

all of them

In plain words (Heuristic)

All 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://www.mandiant.com/resources/blog/barracuda-esg-exploited-globally

Sample hashes

Hashes of samples the author lists in the rule's meta (look them up in your threat-intelligence platform).

87847445f9524671022d70f2a812728f

Licence & attribution

Author: Mandiant

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

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: e1eac294-fe60-5bb2-bae4-0f7bcbe6b1db

SIGNATURE_BASE_M_APT_Downloader_BEATDROP
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2022-04-28
SIGNATURE_BASE_APT_NK_MAL_M_Hunting_VEILEDSIGNAL_1
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2023-04-20
SIGNATURE_BASE_APT_NK_MAL_M_Hunting_VEILEDSIGNAL_2
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2023-04-20
SIGNATURE_BASE_APT_NK_MAL_M_Hunting_VEILEDSIGNAL_3
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2023-04-20
SIGNATURE_BASE_APT_NK_MAL_M_Hunting_VEILEDSIGNAL_4
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2023-04-20
SIGNATURE_BASE_APT_NK_MAL_M_Hunting_VEILEDSIGNAL_5
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2023-04-20
SIGNATURE_BASE_APT_NK_MAL_M_Hunting_VEILEDSIGNAL_6
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2023-04-20
SIGNATURE_BASE_APT_UNC4736_NK_MAL_TAXHAUL_3CX_Apr23_1
APT / threat actorSignature Base (Florian Roth / Nextron)· Mandiant· 2023-03-04