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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_3Cxdesktopapp_Macos_Updateagent_Mar23

Detects 3CXDesktopApp MacOS UpdateAgent backdoor component

MalwareSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth (Nextron Systems)
Date
2023-03-30
Modified
2023-12-05
Score / Quality
80 / 85

What this rule detects

Detects 3CXDesktopApp MacOS UpdateAgent backdoor component

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
mal-3cxdesktopapp-macos-updateagent-mar23.yarDetection Rule License 1.1
rule SIGNATURE_BASE_MAL_3Cxdesktopapp_Macos_Updateagent_Mar23 : FILE
{
	meta:
		description = "Detects 3CXDesktopApp MacOS UpdateAgent backdoor component"
		author = "Florian Roth (Nextron Systems)"
		id = "596eb6d0-f96f-5106-ae67-9372d238e4cf"
		date = "2023-03-30"
		modified = "2023-12-05"
		reference = "https://twitter.com/patrickwardle/status/1641692164303515653?s=20"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/gen_mal_3cx_compromise_mar23.yar#L330-L354"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "9e9a5f8d86356796162cee881c843cde9eaedfb3"
		logic_hash = "0818a8f0b59a9baaefaa0b505f8261e0e0df283e79da8e95dc71e9afdca224ab"
		score = 80
		quality = 85
		tags = "FILE"

	strings:
		$a1 = "/3CX Desktop App/.main_storage" ascii
		$x1 = ";3cx_auth_token_content=%s;__tutma=true"
		$s1 = "\"url\": \"https://"
		$s3 = "/dev/null"
		$s4 = "\"AccountName\": \""

	condition:
		uint16( 0 ) == 0xfeca and filesize < 6MB and ( 1 of ( $x* ) or ( $a1 and all of ( $s* ) ) ) or all of them
}

Strings (5 patterns)

IdentifierTypeValueModifiers
$a1text"/3CX Desktop App/.main_storage"ascii
$x1text";3cx_auth_token_content=%s;__tutma=true"
$s1text"\"url\": \"https://"
$s3text"/dev/null"
$s4text"\"AccountName\": \""

Condition

uint16( 0 ) == 0xfeca and filesize < 6MB and ( 1 of ( $x* ) or ( $a1 and all of ( $s* ) ) ) or all of them

In plain words (Heuristic)

  • The file must be smaller than 6MB (a cheap guard that skips large files).
  • All patterns in ( $s* ) must match.
  • All patterns in the rule must match.
  • At least 1 patterns in ( $x* ) must match.
  • Pattern $a1 must be present.

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References

Sample hashes

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

  • 9e9a5f8d86356796162cee881c843cde9eaedfb3

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: 596eb6d0-f96f-5106-ae67-9372d238e4cf

Tags:FILE

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