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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_Chrysalis_Dllloader_Feb26

Detects DLL used to load Chrysalis backdoor, seen being used in the compromise of the infrastructure hosting Notepad++ by Chinese APT group Lotus Blossom

MalwareChrysalisDllloaderSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
X__Junior
Date
2026-02-02
Modified
2026-05-15
Score / Quality
80 / 85

What this rule detects

Detects DLL used to load Chrysalis backdoor, seen being used in the compromise of the infrastructure hosting Notepad++ by Chinese APT group Lotus Blossom

Associated malware family: Chrysalis, Dllloader.

Targets: Windows PE.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
mal-chrysalis-dllloader-feb26.yarDetection Rule License 1.1
rule SIGNATURE_BASE_MAL_Chrysalis_Dllloader_Feb26 : FILE
{
	meta:
		description = "Detects DLL used to load Chrysalis backdoor, seen being used in the compromise of the infrastructure hosting Notepad++ by Chinese APT group Lotus Blossom"
		author = "X__Junior"
		id = "a2bf8cde-36a5-565d-9257-f1a4b2d67adc"
		date = "2026-02-02"
		modified = "2026-05-15"
		reference = "https://www.rapid7.com/blog/post/tr-chrysalis-backdoor-dive-into-lotus-blossoms-toolkit/"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/lotusblossom_notepad_exploitation.yar#L1-L15"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "3bdc4c0637591533f1d4198a72a33426c01f69bd2e15ceee547866f65e26b7ad"
		logic_hash = "5e118287bd048788a746d412d00ddd2596224b30562d66c4441738fcc09cee87"
		score = 80
		quality = 85
		tags = "FILE"

	strings:
		$op1 = { 33 D2 8B C1 F7 F6 0F B6 C1 03 55 ?? 6B C0 ?? 32 02 88 04 0F 41 83 F9 ?? 72 }
		$op2 = { 0F B6 04 31 41 33 C2 69 D0 ?? ?? ?? ?? 3B CB 72 }

	condition:
		uint16( 0 ) == 0x5a4d and all of them
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$op1hex{ 33 D2 8B C1 F7 F6 0F B6 C1 03 55 ?? 6B C0 ?? 32 02 88 04 0F 41 83 F9 ?? 72 }
$op2hex{ 0F B6 04 31 41 33 C2 69 D0 ?? ?? ?? ?? 3B CB 72 }

Condition

uint16( 0 ) == 0x5a4d and all of them

In plain words (Heuristic)

  • The file must start with “MZ” — a Windows executable (PE).
  • All 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).

  • 3bdc4c0637591533f1d4198a72a33426c01f69bd2e15ceee547866f65e26b7ad

Licence & attribution

Author: X__Junior

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: a2bf8cde-36a5-565d-9257-f1a4b2d67adc

Tags:FILE

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