Bitdefender has developed a free Bart ransomware decryptor that allows victims to unlock their files without paying a ransom.

Bart Ransomware was first detected in June 2016. The ransomware variant stood out from the many others due to its ability to encrypt files even without an Internet connection. Most ransomware variants rely on a connection to their command and control server to generate public-private key pairs; however, Bart ransomware does not. Only the decryption process requires an Internet connection to transfer the ransom payment and receive the decryption key.

Bart ransomware posed a significant threat to corporate users. Command and control center communications could potentially be blocked by firewalls preventing encryption of files. However, without any C&C contact, corporate users were at risk.

Bart ransomware was believed to have been developed by the gang behind Locky and the Dridex banking Trojan. Bart ransomware shared a significant portion of code with Locky, was distributed in the same manner and used a ransom message very similar to that used by Locky.

As with Locky, Bart ransomware encrypted a wide range of file types. While early versions of the ransomware variant were fairly unsophisticated, later versions saw flaws corrected. Early versions of the ransomware variant blocked access to files by locking them in password-protected zip files.

The initial method of locking files was ‘cracked’ by AVG, although only by guessing the password using brute force methods. In order for the brute force method to work, a copy of an encrypted file along with its unencrypted original was required. In later versions of the ransomware, the use of zip files was dropped and AVG’s decryption technique was rendered ineffective. The encryption process used in the later versions was much stronger and the ransomware had no known flaws.

Until Bitdefender developed the latest Bart Ransomware decryptor, victims had two choices – recover encrypted files from backups or pay the attackers’ ransom demand.

Fortunately, Bitdefender was able to create a Bart Ransomware decryptor from keys supplied by Romanian police which were obtained during a criminal investigation. The Bart ransomware decryptor was developed by Bitdefender after collaborating with both the Romanian police and Europol.

From April 4, 2017, the Bart ransomware decryptor has been made available for free download from the No More Ransom website. If your files have been encrypted by ransomware, it is possible to tell if the culprit is Bart from the extension added to encrypted files. Bart uses the .bart, .perl, or extensions.

Bart ransomware may be believed to have links to Locky, although there is no indication that keys have been obtained that will allow a Locky ransomware decryptor to be developed. The best form of defense against attacks is blocking spam emails to prevent infection and ensuring backups of all sensitive data have been made.