W32/Kryptik.FWMX!tr.ransom is a generic detection for a Locky Ransomware trojan. Since this is a generic detection, malware that are detected as W32/Kryptik.FWMX!tr.ransom may have varying behaviour.
Below are examples of some of these behaviours:

  • This ransomware is usually dropped by VBA/Agent.EDD!tr.dldr.

  • This malware will drop lukitus-[Random].htm all over the affected hosts that serves as the ransom notes.

  • Based on our tests this Ransomware usually resides as undefinedAppDataundefined\Local\Temp[Random].exe.

  • This malware will also drop undefinedUserundefined\Desktop\lukitus.bmp, another ransom note for the affected user.

  • The following registry modifications are applied:
    • HKEY_CURRENT_USER\Control Panel\Desktop
      • Wallpaper = "undefinedUserundefined\Desktop\lukitus.bmp"
      The value filled in this registry will reflect as the affecter user's desktop Wallpaper.

  • Encrypted files are renamed using the filename format XXXXXXXX-XXXX-XXXX-XXXXXXXX-XXXXXXXXXXXX.lukitus, where X is any alphanumeric character.

  • Below is an example of the Ransom notes:

    • Figure 1: Ransom notes.

    • Figure 2: Ransom notes.

Recommended Action

  • Make sure that your FortiGate/FortiClient system is using the latest AV database.
  • Quarantine/delete files that are detected and replace infected files with clean backup copies.