Threat Management, Malware

Version 4.0 of ransomware Cryptowall released, now encrypts file names

Reporting on a new strain of Cryptowall, the ransomware trojan,'s editor Lawrence Abrams has reported on why the new version is more powerful than before and poses a security threat that at present has no resolution.

Abrams became aware of the new Cryptowall variant when looking into cases where people reported they had been infected by what was called the help_your_files ransomware. He quickly determined that this was in fact a new version of CryptoWall.

According to Abrams, one of the biggest changes is that when the files are encrypted, the file names are encrypted, too, with names like 27p9k967z.x1nep or 9242on6c.6la9. This is presumably to frustrate those infected even more, not being able to know what data they should be saving.

The other major change is a redesign of the HTML ransom note along with changing its name to help_your_files.html. Abrams reports a general sense of arrogance in the wording that is meant to even further annoy infected users and push them into paying the ransom.

CryptoWall continues to be distributed via email attachments. Abrams reported that in the infections analysed, the file was pretending to be a CV inside a zipped e-mail attachment. The CV sent however, is actually a collection of JavaScript files that when executed would download an executable, save it to the Windows %Temp% folder, and then execute it.

Once active, CryptoWall 4.0 will inject itself into Explorer.exe and disable System Restore, delete all Shadow Volume copies, and use bcdedit to turn off Windows Startup Repair. It will then inject itself into svchost.exe and encrypt the data on all local drives, removable drives, and mapped network drives. Once it has completed encrypting your files it will launch the ransom notes that explain what happened and how to purchase the decrypter.

Some quotes from the ransom notes:

Cannot you find the files you need?
Is the content of the files that you have watched not readable?
It is normal because the files' names, as well as the data in your files have been encrypted.
You have become a part of large community CryptoWall.
CryptoWall Project is not malicious and is not intended to harm a person and his/her information data. The project is conducted for the sole purpose of instruction in the field of information security, as well as certification of antivirus products for their suitability for data protection. 
Together we make the Internet a better and safer place.

The Decrypt Service site is still alive in version 4.0 of the malware. From there a victim can make payments, find out the status of a payment, get one free decryption, and create support requests.

At present, there is no way to recover files without restoring from a backup or paying the ransom.

David Emm, Principal Security Researcher at Kaspersky Lab commented: "Given that ransomware offers such a lucrative return on investment for cyber-criminals, the appearance of CryptoWall 4.0 isn't surprising. At Kaspersky Lab, we have seen a growth in this sort of malware, including mobile ransomware programs.

"In addition to blocking ransomware, we work with law enforcement agencies to help them in their efforts to thwart ransomware campaigns. Take, for instance, the recent take down of CoinVault.

"The Police arrested the authors of the botnet, and Kaspersky Lab made available a free tool that enabled victims to decrypt their data."

Emm said Kaspersky would always provide detection for such programs and, where possible, decrypt data. "However, it's vital that businesses and individuals backup regularly, to avoid the risk of losing data.When it comes to the question of paying the ransom, we would recommend not doing so for a couple of reasons. Firstly, there's no guarantee that the criminals will provide decryption keys, and secondly, it validates their business model and encourages the creation of new campaigns," he said. 

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