Key Group: another ransomware group using leaked builders

Key Group, or keygroup777, is a financially motivated ransomware group primarily targeting Russian users. The group is known for negotiating with victims on Telegram and using the Chaos ransomware builder.

The first public report on Key Group’s activity was released in 2023 by BI.ZONE, a cybersecurity solutions vendor: the attackers drew attention when they left an ideological note during an attack on a Russian user, in which they did not demand money. However, according to our telemetry, the group was also active in 2022. Both before and after the attack covered in the BI.ZONE report, the attackers demanded that money be transferred to a Bitcoin wallet.

We tracked Key Group’s activity from the start of their attacks and found that the group used not only Chaos but also other leaked ransomware builders. By analyzing the samples created with their help, we were able to find loaders and malicious URLs on GitHub that showed a connection between the group and previously unknown attackers.

The first variants of ransomware from Key Group’s arsenal were discovered in April 2022. At that time, the group was using the source code of Xorist.

In August 2022, Key Group added the Chaos builder to its toolkit. Notably, on June 30, 2022, the creator of Chaos announced the launch of a RaaS (Ransomware-as-a-Service) partnership program.

In the Chaos variant, a new extension .huis_bn was added to encrypted files, and in the ransom note, the attackers requested that victims send a message on Telegram. This note contained information in both Russian and English and went under the title “HOW TO DECRYPT FILES”:

The next Key Group samples based on Chaos were discovered in January 2023. Throughout the year, the group used this ransomware, primarily changing only the content of the ransom note.

Starting in April 2023, the attackers were active on the DarkStore forum in the dark web. They targeted Telegram channels with spam raids and tested the publicly available remote access Trojan NjRat, which has keylogging, stealing, reverse shell, and USB propagation capabilities.

In the summer of 2023, a new sample of Chaos from Key Group was discovered, named warnep.exe (MD5: C2E1048E1E5130E36AF297C73A83AFF6).

The content of the note was significantly different from previous ones and was of an ideological nature. Key Group no longer provided contact information but declared its motives.

In August 2023, we discovered the group using the Annabelle ransomware (MD5: 05FD0124C42461EF553B4B17D18142F9).

This ransomware is named after the American horror film “Annabelle”. The sample observed in Key Group’s attacks encrypts files and includes an MBR locker (MD5: D06B72CEB10DFED5ECC736C85837F08E), as well as the following built-in evasion techniques.

Disabling Windows Firewall:
Disabling Windows Defender:
Disabling UAC:
Disabling the Registry Editor:
Disabling the Run command from the Windows Start menu:
Modifying Image File Execution Options by setting the RIP value instead of the debugger path for some processes, preventing them from launching correctly:
Deleting shadow copies:

The ransomware adds the .Keygroup777tg.EXE extension to the encrypted files. After encryption, it restarts the computer and displays the following screens:

Around the same time, a sample of the Slam ransomware (MD5: 09CE91B4F137A4CBC1496D3791C6E75B) was detected in Key Group attacks. The Slam builder was also made publicly available back in 2021.

The Slam ransomware uses the AES-CBC encryption algorithm. It also utilizes the IP Logger service to track infected victims.

Upon execution, the ransomware encoded file names using Base64 and added the .keygroup777tg extension.

In September 2023, a wiper based on the RuRansom builder (MD5: 1FED852D312031974BF5EB988904F64E) was found.

RuRansom is a wiper that emerged in 2022 and targets Russia. The malware is written in .NET and uses the AES-CBC encryption algorithm to encrypt files. The Key Group variant is distributed under the name “Россия-обновление.docs.exe” (Russia-update) with a note modified for the group’s objectives:

Around the same time as the Key Group-branded RuRansom instances, a sample of another ransomware, UX-Cryptor, was observed in the attackers’ activities. It is also written in .NET (MD5: 6780495DAD7EB372F1A660811F4894A6).

Instead of encrypting files, this sample terminates the explorer.exe process.

It sets the following text on the current screen using the .NET method System.Windows.Forms.Label.set_Text:

After that, UX-Cryptor additionally saves the ransom note in a file named info-0v92.txt, using output redirection of the echo command:

UX-Cryptor includes several methods for persistence and detection evasion. For example, it overwrites the registry key Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU:

The RunMRU key is used by incident response specialists to examine commands executed through the Run utility.

In February 2024, Key Group switched from Chaos to the Hakuna Matata ransomware (MD5: DA09FCF140D3AAD0390FB7FAF7260EB5). The Hakuna Matata builder was published on the dark web in July 2023.

The Hakuna Matata variant encrypts files using AES-CBC and adds an extension of five random characters. Below is a snippet of Hakuna Matata running in our sandbox.

After encryption, the sample saves a file named keygroup777.txt in the system and refers to it in a message set as the desktop wallpaper:

Contents of the note:

In early March 2024, we discovered a Key Group sample based on the Judge/NoCry ransomware (MD5: 56F5A95FFA6F89C24E0880C519A2AA50).

The NoCry variant encrypts files using AES-256-CBC and adds the .Keygroup777tg extension. The key used for encryption is generated based on the victim’s system data and sent to a C2 server in plain text, allowing the files to be decrypted without the attackers’ involvement.

It’s worth noting that instead of the C2 server address, Key Group provided a link to the Telegram channel hxxps://t[.]me/s/SBUkr, to which the victim’s data and the encryption key were added in the following format:

The channel’s theme is not related to ransomware and consists of political news. This scheme does not involve the attackers obtaining the data.

A complete timeline of Key Group’s use of various ransomware families is presented below.

Delivery and infection

To deliver the Chaos and Xorist ransomware to the victim’s computer, Key Group used multi-stage loaders.

We discovered an LNK file that was likely distributed via phishing emails. The LNK file contained an obfuscated PowerShell command that downloaded an SFX archive (self-extracting archive) from a remote resource:

Deobfuscated command:

Upon extraction, the SFX archive saved another loader to the system. It downloaded another SFX archive containing a sample of the Chaos ransomware (MD5: C910DA0BAA2E08CEFCE079D1F7CB3469), as well as a separate loader that downloaded a sample of the Xorist ransomware (MD5: E0C744162654352F5E048B7339920A76).

The contents of the notes from the two ransomware variants were identical.

In October 2022, we discovered another loader that delivered a variant of Chaos (MD5: F93695564B97F03CC95CA242EDCFB5F8). The loader uses the .NET method WebClient.DownloadData to download the ransomware (MD5: D655E77841CF6DB3008DCD60C9C5EB18) from a GitHub repository:

While studying this repository, we found the already familiar RuRansom wiper, the Hakuna Matata ransomware, as well as a sample of J-Ransomware/LoveYou and the NjRat remote access Trojan.

Persistence methods

Xorist

The first discovered sample of Key Group, the Xorist ransomware, established persistence in the system by changing file extension associations. When a file with the .huis_bn extension, which was added to encrypted files, was opened, the ransomware would launch:

The ransomware also added itself to startup:

Chaos

The Chaos ransomware (MD5: C910DA0BAA2E08CEFCE079D1F7CB3469) copied itself to $user\$appdata\cmd.exe and executed this file as a new process. The new process, in turn, created a new file in the startup folder: $user\$appdata\Microsoft\Windows\Start Menu\Programs\Startup\cmd.url, containing the following:

Annabelle

The Annabelle ransomware added itself to the Run and Winlogon registry keys.

UX-Cryptor

UX-Cryptor added itself to the following registry keys to maintain persistence in the system:

Additionally, it added the following executable file names to startup:

Judge/NoCry

The NoCry sample also has the ability to add itself to the startup folder:

Victims

Key Group primarily targets Russian-speaking users. The ransom notes were often written in Russian or included a translation into Russian.

The .huis_bn extension added to encrypted files in the early versions of Key Group samples, Xorist and Chaos, refers to a Russian-speaking closed group “huis”, known in the shadow community. The group primarily conducted spam raids on Telegram channels. We suspect that Key Group is a subsidiary project of the “huis” group. The group is currently inactive and, according to the latest Telegram post, has been rebranded.

We also checked the GitHub repository from which the ransomware and wipers were downloaded. The account max444432 is subscribed to the account hxxps://github[.]com/json1c. Its description contains the following contact on Telegram: hxxps://t[.]me/json1c.

The Telegram user Bloody-Lord Destroyer-Crew, also known as “bloody” in the shadow community, was the owner of the “huis” group.

In the latest versions of the ransomware, the ransom notes listed the Telegram account @[redacted] (DarkZeus) as a contact, who is one of the administrators of the Key Group channel:

This is a closed Telegram channel. Previously, the group also had an open channel @[redacted], which the attackers used to communicate with victims; however, it is no longer available. In that channel, the group published news about Key Group, updates from other channels of both technical and ideological nature, leaks from other Telegram sources, and announcements about spam raids.

In the GitHub repository used by the attackers to distribute malware, we also found samples of telegram-raid-botnet.exe (Hakuna Matata) and NoCry, uploaded in February 2024. The name of the first sample resonates with the activities of the “huis” group.

Commits for uploading samples to the RMS2 repository

In one of the ransom notes (MD5: 7E1577B6E42D47B30AE597EEE720D3B1), the attackers asked “not to touch Nikita’s channels, bloody and nacha”, which again indicates a connection to “huis”:

Takeaways

As we can see, Key Group, like many hacktivists, does not develop its own malware but actively uses leaked ransomware builders, and the primary C2 channel is a GitHub repository, which makes it easy to track their activities. It’s also important to note that ransomware source code is increasingly becoming publicly available, and the number of groups using leaked builders or ransomware source code is on the rise. In the future, it is likely that there will be even more such groups.

Indicators of compromise

from repository hxxps://raw.githubusercontent[.]com/max444432/RMS2/main/:

URLs
hxxp://fastxstreamz.herokuapp[.]com/913915/ndp462-kb3151800-x86-x64-allos-rus.scr?hash=AgADzh
hxxp://fastxstreamz.herokuapp[.]com/913034/setupdjprog-i0w0w04g8gww4ock.exe?hash=agadox
hxxp://fastxstreamz.herokuapp[.]com/912974/3.exe?hash=agadob
hxxps://raw.githubusercontent[.]com/max444432/RMS2/main/*
make-catherine.at.ply[.]gg – C2 XWorm V2.2