YARA · Volexity threat-intel

VOLEXITY_Susp_Php_Call_User_Func

Webshells using call_user_func() function against an object from a file input or POST variable.

Suspicious / huntingVolexity threat-intelBSD 2-Clause LicenseCompiles with YARA-X

Author: threatintel@volexity.com
Date: 2021-06-16
Modified: 2024-07-30
Score / Quality: 65 / 80

What this rule detects

Webshells using call_user_func() function against an object from a file input or POST variable.

It defines 1 patterns (1 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

susp-php-call-user-func.yarBSD 2-Clause License

rule VOLEXITY_Susp_Php_Call_User_Func : FILE
{
	meta:
		description = "Webshells using call_user_func() function against an object from a file input or POST variable."
		author = "threatintel@volexity.com"
		id = "48c7857e-7dda-5e3f-b82c-7d34c251f083"
		date = "2021-06-16"
		modified = "2024-07-30"
		reference = "https://zhuanlan.zhihu.com/p/354906657"
		source_url = "https://github.com/volexity/threat-intel/blob/3a9d0b52459877ee866a9a0ba06e60059b778c77/2022/2022-06-15 DriftingCloud - Zero-Day Sophos Firewall Exploitation and an Insidious Breach/indicators/yara.yar#L183-L205"
		license_url = "https://github.com/volexity/threat-intel/blob/3a9d0b52459877ee866a9a0ba06e60059b778c77/LICENSE.txt"
		hash = "40b053a2f3c8f47d252b960a9807b030b463ef793228b1670eda89f07b55b252"
		logic_hash = "46c999da97682023861e58f9cd2c8651480db990a0361c1985c6d5c35b5bf0ea"
		score = 65
		quality = 80
		tags = "FILE"
		os = "win,linux"
		os_arch = "all"
		scan_context = "file"
		severity = "high"
		license = "See license at https://github.com/volexity/threat-intel/blob/main/LICENSE.txt"
		rule_id = 5582
		version = 4

	strings:
		$s1 = "@call_user_func(new C()" wide ascii

	condition:
		$s1
}

Strings (1 patterns)

Identifier	Type	Value	Modifiers
$s1	text	"@call_user_func(new C()"	wide ascii

Condition

$s1

In plain words (Heuristic)

Pattern $s1 must be present.

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References

https://zhuanlan.zhihu.com/p/354906657

Sample hashes

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

40b053a2f3c8f47d252b960a9807b030b463ef793228b1670eda89f07b55b252

Licence & attribution

Author: threatintel@volexity.com

Source repository: Volexity threat-intel @ 3a9d0b5245

Licence: BSD 2-Clause License (stated in the rule's own meta)

“See license at https://github.com/volexity/threat-intel/blob/main/LICENSE.txt”

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: 48c7857e-7dda-5e3f-b82c-7d34c251f083

Metadata

os	win,linux
os_arch	all
scan_context	file
severity	high
rule_id	5582
version	4

Tags:FILE

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