Pierluigi Paganini May 18, 2021

Researchers at Tesorion released a decryptor for Judge ransomware that also decrypts files encrypted by the NoCry ransomware.

In January this year, we published a blog post on our analysis of the Judge ransomware. We announced a free decryptor for Judge victims in this blog post, which is available through the NoMoreRansom initiative. Our decryptor has been helping victims to recover their files for free since its release.

After a few months, BleepingComputer wrote about a new variant of the Stupid ransomware, called NoCry. This variant was found by GrujaRS. When we first analyzed the Judge ransomware, we also found the alias: NoCry in the binary. As such, we went ahead to analyze NoCry and determined that it is a variant of Judge as well.

Fortunately, our decryptor for Judge also decrypts files encrypted by the NoCry/Stupid ransomware. In this blog post, we discuss some differences between Judge and NoCry. Furthermore, we confirm that our decryptor also decrypts files affected by NoCry.

Overview

The NoCry ransomware we analyzed is very similar to Judge, the one we previously looked at. It creates a mutex to prevent multiple instances from running in parallel, provides sandbox detection and deletes system restore points. When those tasks are completed, the ransomware starts encrypting the victim’s files. The file encryption process is the same, and therefore, our decryptor can also be used for NoCry.

Some slight differences

Looking closely, there are a couple of interesting differences between NoCry and the Judge ransomware we previously analyzed. For example, the mutex this time is: “rGoB8VnbP6W42hW5”. Furthermore, the screen displayed to the user after file encryption is completed is different.

The screen displayed above is very similar to the one displayed by the WannaCry ransomware. The structure and colors of the screen are similar, and the countdown WannaCry presents is also 72 hours.

We found that the countdown in NoCry is a little bit different from the one presented by Judge. The ransom note screen of the previously analyzed Judge ransomware is displayed below. As we can see, the text above the countdown is: “Time left before the price goes up”. In the NoCry ransomware, the text changed to: “Your files will be lost on”, making the threat more serious.

When these 72 hours pass, the ransomware deletes itself from the infected system. The “Decrypt” button on the ransom note screen is the only way for a victim to restore its files via the intended route. Therefore, once the 72 hours pass, the victim can no longer perform decryption. Using our decryptor however, decryption is still possible.

A free decryptor

The file encryption process did not change, so the decryptor only requires some minor adjustments. Therefore, our current decryptor also decrypts (non-corrupted) files affected by this NoCry/Stupid variant. The decryptor remains free of charge and will be available via the NoMoreRansom initiative soon.

Indicators of Compromise (IoC) are available in the original post at:

https://www.tesorion.nl/en/posts/analysis-of-nocry-a-variant-of-the-judge-ransomware/

About the author: Gijs Rijnders

Malware Researcher & CERT at Tesorion

Follow me on Twitter: @securityaffairs and Facebook

Pierluigi Paganini

(SecurityAffairs – hacking, NoCry ransomware)

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