Kuus ransomware: what it is and how to remove it

From our report of Jul 2020 · not reviewed since

More from our earlier report on Kuus

• Before any attempts to regain access to the personal files, it's a must to remove the ransomware from the machine.
• For this purpose, use a trusted anti-virus program
• Ransomware damage to the system is severe.
• The malware runs a multiplicity of commands via an elevated PowerShell aiming at Registry corruption, disability of system files, startup processes, and more.
• A Variant Of Win32/Kryptik.HEYU (ESET-NOD32)

From our report of Jul 2020 · not reviewed since

Kuus ransomware - a file locking virus that attempts to extort Bitcoin from innocent PC users

Kuus file-encrypting virus is ransomware that has resurfaced in the second half of July 2020.

Detected by the well-known ransomware hunter Michael Gillespie , the ransomware has been proved to be the 241st variant of the STOP/Djvu ransomware family. Just like its predecessors, the malware takes advantage of software cracks, keygens, password unprotected RDPs, and other stealthy infiltration strategies.

If the payload dropper is activated, the ransomware runs a bunch of malicious files, including , f6ff.tmp.exe, c7c6.tmp.exe, and 6AEC.tmp.exe. This group of files is responsible for damaging the system, running the AES-256 encryption algorithm, and taking control over all personal files stored on the infected machine.

If successful, the operation ends up in a complete lock of personal data stored on the system. All pictures, documents, archives, etc. get .kuus file marker and cannot be opened any longer. Ransomware managers provide a sole problem solution - paying the ransom, which is $490 if paid within 72 hours or $980 if later.

.kuus file virus is a ransomware that has been expected as a weekly Djvu ransomware family augmentation. Initially, it's difficult to forecast which variant will be prevailing, but the latest practice with Maas, Zida, Repl, Usam, and others show that the latest releases of this ransomware family are perspective.

Djvu Ransomware virus remains one of the most active viruses since 2019 taking approximately 56% of the active file-encrypting ransomware market. Although variants released before 2019 August can be successfully decrypted using an official decryptor by Emsisoft, the latest variants cannot be cracked by the same decryptor because they are using online keys.

In other words, all the keys provided to the victims are unique and generated in a secure manner, which is why there's no working decryptor for the new versions like the Kuus ransomware virus.

The installation of the ransomware is spotted by the owner of the infected machine because all files (except system files) are encrypted by .kuus extension. Compromised files lose their typical logos, i.e. instead of PDF file logo victim sees a blank logo. Apart from inaccessible files, the ransomware manifests its presence by creating a _readme.txt note on the desktop and many other non-system files. The note says:

The ransomware sample has been uploaded to VirusTotal scanner the day the virus has been released. Based on the results, Kuus removal can be successfully initiated by 47 AV programs out of 72 possible. Typically, the security tool warns the user about the presence of the following infection:

If the system states showing such and similar alerts, do not ignore them. Kuus ransomware removal should be performed immediately to minimize the system damage. Besides, the elimination is needed to start data decryption. However, since the ransomware may run malicious files to block AV tools, you may need to restart the system into Safe Mode with Networking.

As soon as you remove Kuus ransomware, you can pursue with the .kuus file decryption methods. That's the best scenario possible. If, however, you don't have backups, there are several data recovery options.

A full guide on .kuus file recovery is provided at the end of this article. However, before that, make sure to remove the virus using a robust anti-virus and fix the damage that it initiated over the system with tool.

• Trojan.GenericKD.43514787 (B) (Emsisoft)
• W32/Ursnif.DA!tr (Fortinet)
• TrojanSpy.Win32.EMOTET.USXVPGI20 (TrendMicro)
• Trojan:Win32/Glupteba.DSE!MTB (Microsoft), etc.

From our report of Jul 2020 · not reviewed since

Kuus file virus can lock files on the connected external drives

The Kuus virus shows a tendency to widespread.

Right after its detection, victims of this Djvu successor started reporting that the virus managed to lock files on the external drive. Although this fact is currently under investigation by experts, it's most likely that the external drive has been connected to the targeted machine.

The .kuus file recovery on the external drive is the same as on the PC or laptop. If you have a functional decryption key, all files can be decrypted. Otherwise, you can only test the alternative data recovery methods, which may help to return at least some of the locked documents.

From our report of Jul 2020 · not reviewed since

Kuus virus files: limited recovery options

Ransomware, such as the Kuus file virus, is one of the most dangerous computer infections out there.

Since it belongs to the Djvu family, it mainly targets home users rather than corporations and businesses. The developers rely on victims to pay a ransom as soon as they are aware that they cannot open or modify previously-accessible personal data. Since ransomware authors do not care about the wellbeing of their victims, they seek to infect as many people as possible.

The most common misconception about ransomware is that anti-malware software can remove .kuus file extension from the files, and allow users to use them once again. However, they couldn't be more wrong, as security software is not designed for that purpose. Anti-malware is there to free your system from the infection and eliminate the payload of ransomware (e.g., malicious files).

Therefore, do not expect to be able to open .kuus files after you eliminate the infection, as it will not work. Instead, you are left with a very limited set of options that could help you if you are not willing to pay the $490/$980 ransom to criminals.

In most cases, it cannot be decrypted. However, since .kuus files virus belongs to a malware family that is extensive and often scrutinized by various security researchers and AV companies, there are several methods that could help you.

From our report of Jul 2020 · not reviewed since

Using Emsisoft's decryption tool

In case the Kuus file virus used an offline ID to lock your data, there is a chance that Emsisoft's decryptor for Djvu could help you.

Note that this only works after one of the victims pays ransomware authors, regains a decryption key, and then shares it with Emsisoft security researchers. Therefore, it is important to retain encrypted files, even if there is no immediate solution upon infection.

From our report of Jul 2020 · not reviewed since

Third-party recovery tools usage might bring some positive results

While data recovery applications work great when data is accidentally deleted or formatted, they are not as good when it comes to ransomware-encrypted files.

In some situations, however, victims of cryptomalware might be able to restore at least some portion of encrypted data.

From our report of Jul 2020 · not reviewed since

Utilizing built-in Windows resources

It is not surprising that Windows uses automated backup systems, which can be very useful in many situations.

For the purpose, Microsoft employs a system called Shadow Volume Copies. Unfortunately, ransomware developers are well aware of this system and program malware to delete these volumes during the infection process. In case this step fails, users still have chances to recover .kuus files without many troubles.

From our report of Jul 2020 · not reviewed since

STOP ransomware variants most successfully spread through software cracks

Ransomware virus is the prevailing virus type circulating on the Internet for the last couple of years.

Hackers take advantage of inexperienced PC users who fall for various social engineering tricks and unconsciously download file-locking viruses. Unfortunately, the minority of PC users take care of the backups, so ending up with ransomware often pushes them to pay the demanded ransom.

The vast majority of ransomware attacks are initiated via cracked products, such as key generators that are available on torrenting websites, such as The Pirate Bay. Therefore, to protect yourself from virus attacks, do not visit such websites, and stop pirating in any form.

Keep in mind that pirated software is the best target for hackers. In addition to cracks and other pirated content, experts from Dieviren.de warn that criminals can spread ransomware via:

• Email spam attachments. Malicious executables are typically disguised under EXE, Word, PDF, and similar attachments.
• Malvertising. Malicious ads positioned on script-infected websites can run a payload dropper once clicked.
• Fake software updates. People are more and more educated in the technology field, so this method is losing success. Nevertheless, some users still fall for clicking on fake updates saying that some Windows software is out-of-date, Java Flash player or web browser needs updates. Such pop-ups occurring on random websites are fake and should never be trusted. Software updates can be downloaded from official sources only.

From our report of Jul 2020 · not reviewed since

Eliminating Kuus ransomware and recovering the locked files

If you have become a target for hackers, the first thing that you have to do is to remove Kuus virus completely.

This ransomware is dangerous due to a couple of reasons. First of all, it can permanently delete personal files. Second of all, it can run a secondary payload and download other cyber infections, such as Trojan or spyware. Thus, immediate removal is required.

To speed up Kuus removal, restart your machine into Safe Mode and launch a full system scan with a professional anti-virus program. Although you may detect some of the malicious virus files on the system, you are not very likely to be allowed to disable them. Thus, an automatic removal procedure is required with tools like or .

When you successfully remove Kuus virus from Windows, you should check the machine for the damage. For this purpose, try using tool. In case it does not find any affected areas, you can proceed with the data recovery steps listed below.

[GI=method-1]Do not fall for panic if you cannot run the AV scanner. Kuus virus may be running several processes to block security programs. To enable the software, restart the system into Safe Mode with Networking.

[GI=method-2]Previous Windows version might help when trying to deal with ransomware.

As we have already explained, Kuus ransomware virus belongs to the next-gen Djvu versions, which uses unique online keys. Thus, the official decryptor is not available, at least not yet. Nevertheless, we do not recommend paying ransom for criminals. Instead of that, try third-party data recovery methods listed below.

Use Windows Previous Versions feature for data restore

In case third-party software did not help you to retrieve personal files, try to regain access to them using the System Restore feature. (The feature must have been enabled before the attack).

Use Shadow Explorer

Shadow Explorer is not likely to help in this case. The ransomware is set to run the command to delete Shadow Volume Copies. However, you can give this method a try in case the ransomware failed to run the command via the PowerShell successfully.

No official decryptor available.