YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_NK_3CX_Macos_Elextron_App_Mar23_1

Detects macOS malware used in the 3CX incident

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

Author: Florian Roth (Nextron Systems)
Date: 2023-03-31
Modified: 2023-12-05
Score / Quality: 80 / 85

What this rule detects

Detects macOS malware used in the 3CX incident

It defines 4 patterns (4 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-mal-nk-3cx-macos-elextron-app-mar23-1.yarDetection Rule License 1.1

rule SIGNATURE_BASE_APT_MAL_NK_3CX_Macos_Elextron_App_Mar23_1 : FILE
{
	meta:
		description = "Detects macOS malware used in the 3CX incident"
		author = "Florian Roth (Nextron Systems)"
		id = "7a3755d4-37e5-5d3b-93aa-34edb557f2d5"
		date = "2023-03-31"
		modified = "2023-12-05"
		reference = "Internal Research"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/gen_mal_3cx_compromise_mar23.yar#L306-L328"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "51079c7e549cbad25429ff98b6d6ca02dc9234e466dd9b75a5e05b9d7b95af72"
		hash = "f7ba7f9bf608128894196cf7314f68b78d2a6df10718c8e0cd64dbe3b86bc730"
		logic_hash = "00dd28c3edd94e04e35ee9e3a43c30b5a0a1ad21ec8ecf2099bbeb9de2fca8d0"
		score = 80
		quality = 85
		tags = "FILE"

	strings:
		$a1 = "com.apple.security.cs.allow-unsigned-executable-memory" ascii
		$a2 = "com.electron.3cx-desktop-app" ascii fullword
		$s1 = "s8T/RXMlALbXfowom9qk15FgtdI=" ascii
		$s2 = "o8NQKPJE6voVZUIGtXihq7lp0cY=" ascii

	condition:
		uint16( 0 ) == 0xfacf and filesize < 400KB and ( all of ( $a* ) and 1 of ( $s* ) )
}

Strings (4 patterns)

Identifier	Type	Value	Modifiers
$a1	text	"com.apple.security.cs.allow-unsigned-executable-memory"	ascii
$a2	text	"com.electron.3cx-desktop-app"	ascii fullword
$s1	text	"s8T/RXMlALbXfowom9qk15FgtdI="	ascii
$s2	text	"o8NQKPJE6voVZUIGtXihq7lp0cY="	ascii

Condition

uint16( 0 ) == 0xfacf and filesize < 400KB and ( all of ( $a* ) and 1 of ( $s* ) )

In plain words (Heuristic)

The file must be smaller than 400KB (a cheap guard that skips large files).
All patterns in ( $a* ) must match.
At least 1 patterns in ( $s* ) must match.

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

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Sample hashes

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

51079c7e549cbad25429ff98b6d6ca02dc9234e466dd9b75a5e05b9d7b95af72
f7ba7f9bf608128894196cf7314f68b78d2a6df10718c8e0cd64dbe3b86bc730

Licence & attribution

Author: Florian Roth (Nextron Systems)

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: 7a3755d4-37e5-5d3b-93aa-34edb557f2d5

Tags:FILE

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