Nuis ransomware is a type of computer virus that injects your computer, encrypts your files, and then asks to pay the ransom for file decryption. Besides these unpleasant activities, that malware also changes some important settings and can even suspend your antivirus program.
|Damage||All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection.|
|Nuis Removal Tool||To use full-featured product, you have to purchase a license. 6 days free trial available.|
Nuis malware – what is it?
Nuis malware can correctly be classified as a STOP/Djvu virus family. That type of virus is aimed on single users. This feature supposes that Nuis does not bring any type of additional viruses, which usually helps virus of other families to take control of your computer. Since most users do not have anything valuable on their PCs, there is no need to use additional malware that increases the risk of failure of the whole ransomware injection.
The typical signs of this virus activity is the emersion of .nuis files in your folders, instead of the document you used to have. The photo.jpg turns into photo.jpg.nuis, report.xlsx – into report.xlsx.nuis and so on. You are not able to stop this process, and can’t open that documents – they are ciphered with pretty strong algorithm.
You can also see different other signs of virus activity. Suddenly blocked Microsoft Defender and inability to check the well-known anti-malware forums or sites, where the removal and file decryption guides are published. You will see how it works in the paragraph below. The removal and decryption guide are also available – read below how to delete Nuis ransomware and get the .nuis files back.
How did Nuis ransomware encrypt my files?
After the malware injection, the Nuis ransomware creates a connection with its command and control server. This server is commanded by malware maintainers – fraudsters who manage the distribution of this malware. Another activity which is conducted by these crooks is answering the email messages of victims, who want to decrypt their files.
The documents are encrypted with one of the strongest encryption algorithm – AES-256. The digit in the name of this algo means the power of two – 2^256 for this case. 78-digit number of possible decryption keys variations – it is not real to brute force it. As analysts say, it will take more time than our planet can approximately exist, even in case if you make use of the most powerful computer system. In each folder that keeps the encrypted documents, Nuis virus leaves the _readme.txt file with the following contents:
ATTENTION! Don't worry, you can return all your files! All your files like photos, databases, documents and other important are encrypted with strongest encryption and unique key. The only method of recovering files is to purchase decrypt tool and unique key for you. This software will decrypt all your encrypted files. What guarantees you have? You can send one of your encrypted file from your PC and we decrypt it for free. But we can decrypt only 1 file for free. File must not contain valuable information. You can get and look video overview decrypt tool: https://we.tl/t-WJa63R98Ku Price of private key and decrypt software is $980. Discount 50% available if you contact us first 72 hours, that's price for you is $490. Please note that you'll never restore your data without payment. Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours. To get this software you need write on our e-mail: email@example.com Reserve e-mail address to contact us: firstname.lastname@example.org Your personal ID: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
However, you can still run some of your files. The Nuis malware encrypts only the first 150 KB of each file, but the rest of this document can be accessed. Primarily, it works best with audio/video files, which are definitely bigger than 150 kilobytes. Not each media player is capable of open these files – WinAmp is the best option, since it is free and well-tested. First seconds of each song or video will be missing – this part is encrypted – but the rest of the file will be accessible like nothing happened.
Is Nuis ransomware dangerous for my PC?
As it was mentioned several paragraphs above, ransomware is not only about encrypting the files. Nuis virus makes the changes in your system in order to prevent searching the malware removal and file decryption guides. Malware does not establish the software obstacle – it just changes the system settings, primarily – networking and security configurations.
Through the networking configurations, the most changed item is the HOSTS file. This text file keeps the DNS-address instructions, which are used by the web browsers while sending a request to the server. If you add a specific DNS-address for the certain website, your web browser will connect that page through that DNS next time. Ransomware modifies that file, adding the non-existent DNS, so any of the web browsers will show you the “Unable to resolve the DNS-address” error.
Other alterations done by the ransomware are aimed at prevention of early detection of itself, and also preventing the installation of the majority of antivirus programs. Nuis ransomware implements some changes in Group Policies – the system configuration app which allows to alter the abilities of each app. In such a way, the virus disables the Microsoft Defender and different other antivirus tools, and also disables the launch of anti-malware installation files.
How did I get infected?
Throughout the whole term while STOP/Djvu family existed, it was using questionable software as a primary method of ransomware injection. Under the term of questionable applications I mean apps that are already not supported by the maintainer and spread through the third-party websites. These programs may be hacked, to make them possible to use without purchasing any license. One more example of such a program class is different hacking tools – cheat engines, keygens, Windows activation tools and so on.
This sort of apps may be distributed in many methods – through the website that offers a downloading link, or through the p2p networks – ThePirateBay, eMule and so on. All these sources are well-known as the most popular computer piracy sites. People use these sources to get different apps or games for free, even if they must be purchased. No one can stop the users who hack these programs from adding malware of some sort to the files of the hacked app. Hacktools, meanwhile, are created for outlaw targets, so their developers can easily insert the virus under the guise of some program part.
These hacked programs, regardless of their source, are one of the most often sources for various viruses, and 100% the most used one for Nuis ransomware. It is better to stop making use of it, and not only because of virus spreading risks. Avoiding the license purchase is an outlaw action, and both hackers and users who use cracked apps fall under the charge of piracy.
How do I remove Nuis virus?
The Nuis virus is extremely hard to remove manually. In fact, because of the amount of changes it makes into your PC, it is almost unreal to spot them all and fix. The best decision is to use anti-malware programs. But which one to choose?
You may read the advices to use Microsoft Defender, which is already in your system. Nonetheless, as it was mentioned earlier, the majority of STOP/Djvu malware examples stop it even before the encryption procedure. Making use of the third-party application is the only solution – and I can advice you the GridinSoft Anti-Malware as an option for that case. It has perfect detection abilities, so the virus will not be missed. It is also capable of system repairing, which is heavily needed after the Nuis virus attack.
To remove Nuis malware infections, scan your computer with legitimate antivirus software.
After the ransomware removal, you can go to file decryption. Malware removal is needed to prevent the repeating encryption of your files: while Nuis ransomware is active, it will not pass any unencrypted file.
How to decrypt the .nuis files?
There are two ways to decrypt your files after a Nuis malware attack. First one and the most popular is file decryption. It is conducted with a special program, designed by Emsisoft, and called Emsisoft Decryptor for STOP/Djvu. This program is free. Analysts update its decryption keys databases as often as possible, so you will definitely get your files back, sooner or later.
Another way to get your documents and photos back is to try to recover them from your physical disks. Since ransomware deletes them and substitutes with an encrypted copy, the residue of the documents are still kept on the disk. After the deletion, the information about them is removed from the file system, but not from a disk. Special programs, like PhotoRec, are able to recover these files. It is free, too, and may also be used for file recovery in case when you have deleted some files unintentionally.
Decrypting the .nuis files with Emsisoft Decrypter for STOP/Djvu
Download and install Emsisoft Decrypter tool. Agree with its EULA and continue to the interface.
The interface of this program is extremely easy. All you have to do is to select the folder where the encrypted files are stored, and wait. If the program has the decryption key which corresponds to your ransomware case – it will decrypt it.
During the use of Emsisoft Decrypter for STOP/Djvu, you may observe various error messages. Don’t worry, that does not mean that you did something wrong or a program does not work properly. Each of these errors refer to a specific case. Here is the explanation:
Error: Unable to decrypt file with ID: [your ID]
The program does not have a corresponding key for your case. You need to wait for some time until the key database will be updated.
No key for new variant online ID: [your ID]
Notice: this ID appears to be an online ID, decryption is impossible.
This error means that your files are encrypted with an online key. In such a case, the decryption key is unique and stored on the remote server, controlled by crooks. Unfortunately, the decryption is impossible.
Result: No key for new variant offline ID: [example ID]
This ID appears to be an offline ID. Decryption may be possible in the future.
Ransomware uses the offline key to encrypt your files. This key is not unique, so you likely have it in common with another victim. Since offline keys must be collected, too, it is important to keep calm and wait until the analysts team finds one which will fit your case.
Remote name could not be resolved
This error indicates that the program has problems with DNS on your computer. That’s a clear sign of malicious alterations in your HOSTS file. Reset it using the official Microsoft guide.
Recovering the .nuis files with PhotoRec tool
PhotoRec is an open-source tool, which is designed to recover the deleted or lost files from the disk drive. It checks each disk sector for the residues of deleted files, and then tries to recover them. That app is able to recover the files of more than 400 different formats. Because of the described feature of ransomware encryption mechanism, it is possible to use this tool to get the original, unencrypted files back.
Download PhotoRec from the official website. It is absolutely free, however, its developer warns that he does not guarantee that this program will be 100% effective for file recovery purposes. Moreover, even paid apps can barely give you such a guarantee, because of the chain of random factors that can make the file recovery harder.
Unzip the downloaded archive to the folder you like. Don’t worry because of its name – TestDisk – this is the name of the utility developed by the same company. They decided to spread it together since PhotoRec and TestDisk are often used together. Among the unzipped files, search for qphotorec_win.exe file. Run this executable file.
Before you can start the recovery process, you need to specify several settings. In the drop-down list, choose the logic disk where the files were stored before the encryption.
Then, you need to specify the file formats you need to recover. It may be difficult to scroll all 400+ formats, luckily, they are sorted by alphabetical order.
Finally, name the folder you want to use as a container for recovered files. The program will likely dig out a lot of useless files, which were deleted intentionally, so desktop is a bad solution. The best option is to use the USB-drive.
After these easy manipulations, you may just press the “Search” button (it turns active if you specified all required parameters). The recovery process may take several hours, so keep patient. It is recommended not to use the computer during this term, since you may overwrite some files you are intending to recover.
Frequently Asked Questions
✔️Are the files encrypted by Nuis ransomware dangerous?
No. Nuis files is not a virus, it is not able to inject its code into the files and force them to execute it. The .EXT files are just the same as regular ones, but encrypted and cannot be opened in the usual way. You may store it together with normal files without any fears.
✔️Is it possible that antivirus software will delete the encrypted files?
As I have mentioned in a previous paragraph, encrypted files are not dangerous. Hence, good anti-malware programs like GridinSoft Anti-Malware will not trigger on them. Meanwhile, some of the “disk cleaning tools” may remove them, stating that they belong to the unknown format and are likely broken.
✔️The Emsisoft tool says my files are encrypted with the online key and cannot be decrypted. What do I need to do?
It is very unpleasant to hear that the files you have are likely lost. Ransomware creators lie a lot in order to scare their victims, but they tell the truth in claims about the strength of the encryption. Your decryption key is stored on their servers, and it is impossible to select it because of the strength of the encryption mechanism.
Try other recovery methods – through the PhotoRec, or using the previously created backups. Search for the previous versions of these files – getting back a part of your dissertation, for example, is better than missing it all.
Last option is just waiting. When the cyber police caughts the crooks who create and distribute ransomware, first get the decryption keys and publish it. Emsisoft analysts will surely take these keys and add them to the Decryptor databases. In some cases, malware creators may publish the rest of the keys when they stop their activity.
✔️Not all of my .nuis files are decrypted. What do I need to do?
The situation when the Emsisoft Decryptor failed to decrypt several files usually happens when you have not added the correct file pair for the certain file format. Another case when this problem may appear is when some problem occurred during the decryption process – for example, RAM limit reached. Try to perform the decryption process once again.
Another situation when the Decryptor app may leave your files unencrypted is when ransomware uses different keys for certain files. For example, it may use offline keys for a short period of time when it has connection issues. The Emsisoft tool is not able to check both key types simultaneously, so you need to launch the decryption again, in order to repeat the process.