A new Dharma ransomware variant has been created that is currently evading detection by most of antivirus engines.

Heimdal Security say that the most recent Dharma ransomware variant captured by its researchers was only identified as malware by one of the 53 AV engines on VirusTotal.

Dharma ransomware (also known as CrySiS) first was seen in 2006 and is still being developed. This year, many new Dharma ransomware variants have been made available, each using new file extensions for encrypted files (.bip, .xxxxx, .like, java, .arrow, .gamma, .arena, .betta, and .tron to name but a few). In the past two months alone four new Dharma ransomware variants have been discovered.

The threat actors to blame for Dharma ransomware have claimed many victims in recent months. Successful attacks have been seen recently by Altus Baytown Hospital in Texas, the Arran brewery in Scotland, and the port of San Diego.

While free decryptors for Dharma ransomware have been created, the constant evolution of this ransomware threat rapidly renders these decryptors obsolete.  Infection with the most recent variants of the ransomware threat only give victims three options: pay a sizeable ransom to recover files, restore files from backups, or face permanent file loss.

The latter is not a solution given the extent of files that are encrypted. Restoring files from backups is not always an option as Dharma ransomware can also encrypt backup files and can erase shadow copies. Payment of a ransom is not a solution as there is no guarantee that files can or will be decrypted.

Safeguarding against ransomware attacks requires a combination of policies, processes, and cybersecurity solutions. Dharma ransomware attacks are mostly carried out via two attack vectors: The exploitation of Remote Desktop protocol (RDP) and via email malspam campaigns.

The most recent Dharma ransomware variant attacks involve an executable file being sent using a .NET file and HTA file. Infections happen using RDP-enabled endpoints using brute force attempts to guess passwords. Once the password is obtained, the malicious payload is activated.

While it is not exactly obvious how the Arran brewery attack happened, a phishing attack is suspected. Phishing emails had been received just before file encryption. Arran Brewery’s managing director Gerald Michaluk said: “We cannot be 100 percent sure that this was the vector that infection occurred through, but the timing seems to be more than coincidental”.

To safeguard against RDP attacks, RDP should be disabled unless it is absolutely necessary. If RDP is a requirement, access should only be possible through a VPN and strong passwords should be established. Rate limiting on login attempts should be set to block login attempts after a set number of failures.

Naturally, good backup policies are vital. They will ensure that file recovery is possible without meeting a ransom. Multiple copies of backups should be made with one copy held securely off site.

To safeguard against email-based attacks, an advanced spam filter is needed. Spam filters that rely on AV engines may not notice the latest ransomware variants. Advanced analyses of incoming messages are vital.

SpamTitan can enhance protection for businesses through combination of two AV engines and predictive techniques to prevent new types of malware whose signatures have not yet been installed on AV engines.

For more information on SpamTitan and safeguarding your email gateway from ransomware attacks and other threats, contact TitanHQ’s security experts today.