rule 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"
      date = "2026-01-29"
      reference = "https://x.com/williballenthin/status/2014687699165135150"
      hash = "ffa48ed4b7b48897f6756c4222b2606399de0bca627cedfddf61e69986580430"
      score = 75
      id = "7a164817-9e90-52f6-a3cb-e6965ee1cc54"
   strings:
      $x1 = "ANTHROPIC_MAGIC_STRING_TRIGGER_REFUSAL_" ascii wide nocase
   condition:
      $x1
}

rule MAL_Claude_Refusal_Magic_String_Jan26 {
   meta:
      description = "Detects Base64 variations of 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"
      date = "2026-01-29"
      reference = "Internal Research"
      score = 80
      id = "8f0351b7-56b8-5059-8c1e-e8d87fa0ca91"
   strings:
      $xb1 = "ANTHROPIC_MAGIC_STRING_TRIGGER_REFUSAL_" ascii wide base64 base64wide
   condition:
      $xb1
}

rule SUSP_Claude_Redacted_Thinking_Magic_String_Jan26_1 {
   meta:
      description = "Detects redacted thinking 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"
      date = "2026-01-29"
      reference = "Internal Research"
      hash = "ffa48ed4b7b48897f6756c4222b2606399de0bca627cedfddf61e69986580430"
      score = 65
      id = "623de3f9-ea03-5b6a-bb24-14b4a6d4a7c9"
   strings:
      $x1 = "ANTHROPIC_MAGIC_STRING_TRIGGER_REDACTED_THINKING_" ascii wide nocase
   condition:
      $x1
}

rule SUSP_Claude_Redacted_Thinking_Magic_String_Jan26_2 {
   meta:
      description = "Detects Base64 variations of redacted thinking 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"
      date = "2026-01-29"
      reference = "Internal Research"
      score = 75
      id = "453ad61a-838f-529a-b119-1dd3ec559069"
   strings:
      $xb1 = "ANTHROPIC_MAGIC_STRING_TRIGGER_REDACTED_THINKING_" ascii wide base64 base64wide
   condition:
      $xb1
}