A new ransomware dubbed as “GIBON”  was spotted by the ProofPoint researcher Matthew Mesa that observed it being distributed by malware spam.

The researcher dubbed the ransomware “GIBON” because of the presence of the string in two places:

  • User-Agent String of the malware containing the string “GIBON” while it communicating with its Control & Command Center
  • Admin panel for the ransomware’s C&C Server. (the logo is from the Russian television company VID)

The spam messages use a malicious document as attachment containing macros that once enabled will download and install the ransomware on a victim’s machine.

 

Operation:

Step#1:

When the GIBON malware executes, it connects to the C&C server and registers the new victim by sending a base64 encoded string that contains the timestamp, the version of Windows, and the “register” string.

Step#2: 

The C&C Server in turn, sends back a response that contains a base64 encoded string that will be used by GIBON ransomware as the ransom note

Step#3: 

Once the infected machine is registered with the C&C,  it will locally generate an encryption key and send it to the server as a base64 encoded string. The malware will use the key to encrypt all files on the target computer, it appends the .encrypt extension to the encrypted file’s name

Step#4: 

Now that the victim has been registered and key transmitted to the C2, the ransomware will begin to encrypt the computer. While encrypting the computer, it will target all files regardless of the extension as long as they are not in the Windows folder.” reads the blog post published by Lawrence Abrams

During the encryption process, GIBON will routinely connect to the C2 server and send it a “PING” to indicate that it is still encrypting the computer

Step#5: 

The malware drops a ransom note in each folder containing the encrypted files, it also generates a ransom note named READ_ME_NOW.txt.

Attention! All the files are encrypted! 
To restore the files, write to the mail:bomboms123@mail.ru 
If you do not receive a response from this mail within 24 hours, 
then write to the subsidiary:yourfood20@mail.ru”

Step#6: Once the GIBON ransomware completes the file encryption the victim’s computer, it will send a message to the C&C server with the string “finish”, a timestamp, the Windows version, and the number of  files that were encrypted.

GOOD NEWS:

The files encrypted by this ransomware can be decrypted using the GibonDecrypter.

Sources: bleepingcomputer.com, securityaffairs.co

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