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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_SUSP_Claude_Refusal_Magic_String_Jan26

Detects refusal magic string that cause Claude sessions to be terminated. This might indicate that a file tries to prevent being analyzed by LLM agents.

Suspicious / huntingSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Marius Benthin
Date
2026-01-29
Modified
2026-05-15
Score / Quality
75 / 83

What this rule detects

Detects refusal magic string that cause Claude sessions to be terminated. This might indicate that a file tries to prevent being analyzed by LLM agents.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
susp-claude-refusal-magic-string-jan26.yarDetection Rule License 1.1
rule SIGNATURE_BASE_SUSP_Claude_Refusal_Magic_String_Jan26
{
	meta:
		description = "Detects refusal magic string that cause Claude sessions to be terminated. This might indicate that a file tries to prevent being analyzed by LLM agents."
		author = "Marius Benthin"
		id = "7a164817-9e90-52f6-a3cb-e6965ee1cc54"
		date = "2026-01-29"
		modified = "2026-05-15"
		reference = "https://x.com/williballenthin/status/2014687699165135150"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/susp_claude_magic_strings.yar#L1-L14"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "ffa48ed4b7b48897f6756c4222b2606399de0bca627cedfddf61e69986580430"
		logic_hash = "ae5b451168d03440f84b89d96db2688f828e5dcbcdd1121edf3fb973571d2dbd"
		score = 75
		quality = 83
		tags = ""

	strings:
		$x1 = "ANTHROPIC_MAGIC_STRING_TRIGGER_REFUSAL_" ascii wide nocase

	condition:
		$x1
}

Strings (1 patterns)

IdentifierTypeValueModifiers
$x1text"ANTHROPIC_MAGIC_STRING_TRIGGER_REFUSAL_"ascii wide nocase

Condition

$x1

In plain words (Heuristic)

  • Pattern $x1 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).

  • ffa48ed4b7b48897f6756c4222b2606399de0bca627cedfddf61e69986580430

Licence & attribution

Author: Marius Benthin

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: 7a164817-9e90-52f6-a3cb-e6965ee1cc54

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