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SEKOIA_Tool_Webshell_B374K_Strings

Detects b374k webshell

Hack toolSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X
Author
Sekoia.io
Date
2024-09-06
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Detects b374k webshell

It defines 2 patterns (2 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
tool-webshell-b374k-strings.yarDetection Rule License 1.1
rule SEKOIA_Tool_Webshell_B374K_Strings : FILE
{
	meta:
		description = "Detects b374k webshell"
		author = "Sekoia.io"
		id = "f53fc668-e1fc-4b85-b850-59aceefb6418"
		date = "2024-09-06"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/tool_webshell_b374k_strings.yar#L1-L21"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		hash = "1d27b23fceecbb9e854c41f6a8fb878e"
		hash = "71fd853a3f3efc3dc2846e866187ee59"
		hash = "187e001c32487d0d68197ddb7e7796c3"
		hash = "6eac497dfc1020a8475e95542fad197e"
		hash = "61c6a0bc15efa442853f04bb276ac96e"
		logic_hash = "b085a50d50fc1fd06d6f75397cf1fa6fa1bc4a0d18b56ed3458990f4abde0632"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$ = "$func('$x','ev'.'al'.'("
		$ = "(ba'.'se'.'64'.'_de'.'co'.'de($x)))"

	condition:
		2 of them and filesize < 1MB
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$text"$func('$x','ev'.'al'.'("
$text"(ba'.'se'.'64'.'_de'.'co'.'de($x)))"

Condition

2 of them and filesize < 1MB

In plain words (Heuristic)

  • The file must be smaller than 1MB (a cheap guard that skips large files).
  • At least 2 patterns in the rule must match.

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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).

  • 1d27b23fceecbb9e854c41f6a8fb878e
  • 71fd853a3f3efc3dc2846e866187ee59
  • 187e001c32487d0d68197ddb7e7796c3
  • 6eac497dfc1020a8475e95542fad197e
  • 61c6a0bc15efa442853f04bb276ac96e

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: f53fc668-e1fc-4b85-b850-59aceefb6418

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE

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