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SEKOIA_Apt_Toneshell_Shellcode

Detects first bytes of ToneShell used to call the shellcode or the code to check the MagicNumber (0x17 0x03 0x03)

APT / threat actorSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X
Author
Sekoia.io
Date
2024-10-02
Modified
2024-12-19
Score / Quality
75 / 80

What this rule detects

Detects first bytes of ToneShell used to call the shellcode or the code to check the MagicNumber (0x17 0x03 0x03)

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

Summary generated from the rule's metadata and condition.

Rule source

apt-toneshell-shellcode.yarDetection Rule License 1.1
rule SEKOIA_Apt_Toneshell_Shellcode : FILE
{
	meta:
		description = "Detects first bytes of ToneShell used to call the shellcode or the code to check the MagicNumber (0x17 0x03 0x03)"
		author = "Sekoia.io"
		id = "5ac8d2e9-dbeb-42f9-8343-1281510d4411"
		date = "2024-10-02"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/apt_toneshell_shellcode.yar#L1-L34"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "0e164677681dce2aa75d3621d9f3df1449c3e67a3551817693856d80ccc48eca"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$code = {55 8b ec 83 ec 0c e8 85 00 00 00 6a 00 6a 00 6a 02 6a 00 6a 00 68 00 00 00 10}
		$MagicNumberParser = {
        B8 01 00 00 00
        6B C8 00
        8B 55 ??
        0F BE 04 0A
        83 F8 17
        75 ??
        B9 01 00 00 00
        C1 E1 00
        8B 55 ??
        0F BE 04 0A
        83 F8 03
        75 ??
        B9 01 00 00 00
        D1 E1
        8B 55 ??
        0F BE 04 0A
        83 F8 03
        }

	condition:
		any of them and filesize < 1MB
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$codehex{55 8b ec 83 ec 0c e8 85 00 00 00 6a 00 6a 00 6a 02 6a 00 6a 00 68 00 00 00 10}
$MagicNumberParserhex{ B8 01 00 00 00 6B C8 00 8B 55 ?? 0F BE 04 0A 83 F8 17 75 ?? B9 01 00 00 00 C1 E1 00 8B …

Condition

any 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 one pattern in the rule must match.

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References

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: 5ac8d2e9-dbeb-42f9-8343-1281510d4411

Metadata

version1.0
classificationTLP:CLEAR

Tags:FILE