MAL_Sindoor_Decryptor_Aug25

rule MAL_Sindoor_Decryptor_Aug25 {
   meta:
      description = "Detects AES decryptor used by Sindoor dropper related to APT 36"
      author = "Pezier Pierre-Henri"
      date = "2025-08-29"
      score = 80
      reference = "Internal Research"
      hash = "9a1adb50bb08f5a28160802c8f315749b15c9009f25aa6718c7752471db3bb4b"
      id = "3c0c5217-b125-51a3-8129-30af5f0c7263"
   strings:
      $s1 = "Go build"
      $s2 = "main.rc4EncryptDecrypt"
      $s3 = "main.processFile"
      $s4 = "main.deriveKeyAES"
      $s5 = "use RC4 instead of AES"
   condition:
      filesize < 100MB
      and (
         uint16(0) == 0x5a4d // Windows
         or uint32be(0) == 0x7f454c46  // Linux
         or (uint32be(0) == 0xcafebabe and uint32be(4) < 0x20)  // Universal mach-O App with dont-match-java-class-file hack
         or uint32(0) == 0xfeedface  // 32-bit mach-O
         or uint32(0) == 0xfeedfacf  // 64-bit mach-O
      )
      and all of them
}