MSIL/FilecoderEnc.E3FD!tr.ransom

Analysis

MSIL/FilecoderEnc.E3FD!tr.ransom is a detection for a Ransomware trojan.
Below are some of its observed characteristics/behaviours:

• Part of the malware's antidebugging strategy is to check if its currently running on a Virtualized Environment then displays a message if it detected so.



Figure 1: Testing VM.




Figure 2: Prompt for running in VM.



• This malware utilizes AES algorithm to encrypt the files.



Figure 3: AES Encryption.



• The malware code below indicates that it might had bundled a decryption along with a corresponding message box.



Figure 4: Decryption function.




Figure 5: Decryption message box.




Figure 6: Decryption message code.



• Affected files of this Ransomware will use the filenaming format {original name}.enc.



Figure 7: Affected files extension used.



• Below is a code indicating the flag used/set to avoid re-encrypting victim users that might have paid the Ransom amount.



Figure 8: Flag used/set.



• Below is a sample illustration of the raw Ransom notes and other targeted user information:
  

  Figure 9: 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.