November 14, 2017
Today, I discovered a new variant of the CryptoMix Ransomware being distributed that is appending the .XZZX extension to encrypted file names.
This article will provide a brief summary on any changes that have occurred in this new variant. As we are always looking for weaknesses, if you are a victim of this variant and decide to pay the ransom, please send us the decryptor so we can take a look at it. You can also discuss or receive support for Cryptomix ransomware infections in our dedicated Cryptomix Help & Support Topic.
Changes in the XZZX Cryptomix Ransomware Variant
XZZX CryptoMix Ransom Note
The next noticeable change is the extension appended to encrypted files. With this version, when a file is encrypted by the ransomware, it will modify the filename and then append the .XZZX extension to encrypted file's name. For example, a test file encrypted by this variant has an encrypted file name of 0D0A516824060636C21EC8BC280FEA12.XZZX.
Folder of Encrypted XZZX Files
This variant also contains 11 public RSA-1024 encryption keys that will be used to to encrypt the AES key used to encrypt a victim's files. This allows the ransomware to work completely offline with no network communication. This variant's 11 public RSA keys are the same as the previous XZZX Cryptomix Ransomware variant.
As this is just a cursory analysis of this new variant, if anything else is discovered, we will be sure to update this article.
How to protect yourself from the XZZX CryptoMix Ransomware
In order to protect yourself from the XZZX variant of CryptoMix , or from any ransomware, it is important that you use good computing habits and security software. First and foremost, you should always have a reliable and tested backup of your data that can be restored in the case of an emergency, such as a ransomware attack.
You should also have security software that contains behavioral detections such as Emsisoft Anti-Malware or Malwarebytes. Regardless of the security software you use, make sure it contains behavioral detections so you do not have to rely on signatures or heuristics.
Last, but not least, make sure you practice the following good online security habits, which in many cases are the most important steps of all:
- Backup, Backup, Backup!
- Do not open attachments if you do not know who sent them.
- Do not open attachments until you confirm that the person actually sent you them,
- Scan attachments with tools like VirusTotal.
- Make sure all Windows updates are installed as soon as they come out! Also make sure you update all programs, especially Java, Flash, and Adobe Reader.
- Older programs contain security vulnerabilities that are commonly exploited by malware distributors. Therefore it is important to keep them updated.
- Make sure you use have some sort of security software installed.
- Use hard passwords and never reuse the same password at multiple sites.