Webshell_FOPO_Obfuscation_APT_ON_Nov17_1

rule Webshell_FOPO_Obfuscation_APT_ON_Nov17_1 {
   meta:
      description = "Detects malware from NK APT incident DE"
      license = "Detection Rule License 1.1 https://github.com/Neo23x0/signature-base/blob/master/LICENSE"
      author = "Florian Roth (Nextron Systems)"
      reference = "Internal Research - ON"
      date = "2017-11-17"
      hash1 = "ed6e2e0027d3f564f5ce438984dc8a54577df822ce56ce079c60c99a91d5ffb1"
      id = "0122bb03-8ff0-554d-8fee-458f0ddd7664"
   strings:
      $x1 = "Obfuscation provided by FOPO" fullword ascii

      $s1 = "\";@eval($" ascii
      $f1 = { 22 29 29 3B 0D 0A 3F 3E }
   condition:
      uint16(0) == 0x3f3c and filesize < 800KB and (
        $x1 or
        ( $s1 in (0..350) and $f1 at (filesize-23) )
      )
}