Oohu malware is a type of computer virus that infiltrates your system, encrypts your documents, and then asks to pay the money for file decryption. Besides these unpleasant actions, that virus also changes some important settings and can even suspend your anti-malware 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.|
|Oohu Removal Tool||To use full-featured product, you have to purchase a license. 6 days free trial available.|
Oohu virus – what is it?
Oohu malware can correctly be described as a STOP/Djvu malware family. That sort of malware is aimed on individuals. This feature supposes that Oohu does not bring any type of additional viruses, which usually helps malware of other families to control your system. Because of the fact that most people do not have anything valuable on their PCs, there is no need to inject additional viruses that increases the risk of failure of the whole ransomware operation.
The usual signs of that virus activity is the appearance of .oohu files in your folders, instead of the document you used to have. The photo.jpg turns into photo.jpg.oohu, report.xlsx – into report.xlsx.oohu and so on. You cannot to stop this action, and can’t open these files – they are encrypted with pretty strong cipher.
You can also see various other signs of ransomware activity. Spontaneously stopped Microsoft Defender and inability to check the well-known anti-malware forums or web pages, where the ransomware removal and file decryption guides are posted. You will see how it is conducted in the paragraph below. The removal and decryption guide are also available – read below how to wipe out Oohu virus and get the .oohu files back.
How did Oohu ransomware encrypt my files?
After the injection, the Oohu virus establishes a connection with its command and control server. This server is commanded by malware maintainers – people who manage the distribution of this malware. Another activity which is conducted by those crooks is answering the emails of sufferers, who want to get their files back.
The documents are encrypted with one of the strongest encryption algorithm – AES-256. The digit in the name of this algorithms means the power of two – 2^256 for this case. 78-digit number of possible decryption password variations – it is unreal to brute force it. As analysts say, it will need more time than our planet can approximately exist, even when you use the most powerful computers. In each folder that has the encrypted documents, Oohu 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
Nevertheless, you can still use some of your files. The Oohu malware ciphers only the initial 150 KB of each file, but the other part of this file can be accessed. Primarily, it works best with audio/video files, which are likely larger 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 every recording will be missing – this part is encrypted – but the rest of the video or music will be accessible like nothing happened.
Is Oohu ransomware dangerous for my PC?
As it was mentioned several paragraphs before, ransomware is not only about encrypting the files. Oohu virus makes the changes in your operating system in order to prevent searching the malware removal and file decryption guides. Malware does not establish the software barrier – it just changes the system settings, primarily – networking and security configurations.
Through the networking settings, the most changed item is the HOSTS configuration file. This text file has the DNS-address instructions, which are used by the browsers while sending a request to the server. If you add a specific DNS-address for the certain website, your browser will connect that website through this DNS next time. Ransomware edits 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 modifications done by the virus are aimed at prevention of fast spotting of itself, and also blocking the installation of the majority of security tools. Oohu virus makes some modifications in Group Policies – the system setting application which allows to change the abilities of each program. In such a way, the virus disables the Microsoft Defender and different other anti-malware apps, and also blocks the launch of antivirus installation files.
How did I get infected?
Throughout the whole term while STOP/Djvu family is active, it was using questionable programs as a primary way of ransomware injection. Under the term of dubious software I mean software that are already not supported by the creator and distributed through the file sharing websites. These applications may be hacked, to make them usable without buying any license. Another example of such a program type is different hacking tools – cheat engines, keygens, Windows activation tools and so on.
This kind of applications may be spread in different methods – through the website that offers a downloading link, as well as through the peer-to-peer networks – ThePirateBay, eMule and so on. All these sources are known as the biggest computer piracy sites. Folks use these sites to get a wide range of apps or games for free, even if these programs must be purchased. Nobody can prevent the users who hack these apps from adding viruses of some type to the files of the hacked tool. Hacktools, however, are created for outlaw purposes, so their creators may easily add the ransomware under the guise of some program element.
These hacked apps, regardless of their source, are one of the most often carriers for various malware, and 100% the most widespread one for Oohu ransomware. The best solution is to avoid using of it, and not only because of malware spreading risks. Avoiding the license buying is an illegal action, and both hackers and persons who use cracked apps fall under the charge of piracy.
How do I remove Oohu virus?
The Oohu malware is very hard to wipe out manually. In fact, because of the number of alterations it makes in your PC, it is almost impossible to find them all and repair. The best solution is to make use of anti-malware software. But which one to choose?
You can see the advices to make use of Microsoft Defender, that is already inside of your Windows. However, as it was mentioned earlier, the majority of STOP/Djvu virus examples block it even before the ciphering process. Making use of the third-party application is the only possible option – and I can advice you the GridinSoft Anti-Malware as a solution for this case. It has perfect detection abilities, so the malware will not be missed. It is also capable of system recovery, that is heavily demanded after the Oohu virus attack.
To remove Oohu malware infections, scan your computer with legitimate antivirus software.
After the ransomware removal, you can go to file decryption. Virus removal is required to prevent the repeating ciphering of your files: while Oohu ransomware is active, it will not pass any unencrypted file.
How to decrypt the .oohu files?
There are two ways to decrypt your files after a Oohu ransomware attack. First one and the most popular is file decryption. It is performed with a special program, designed by Emsisoft, and named Emsisoft Decryptor for STOP/Djvu. This program is absolutely free. Analysts update its decryption keys databases as often as possible, so you will surely get your files back, sooner or later.
Another option to get your documents and photos back is to try to recover them from your disk drives. Since ransomware deletes them and substitutes with a ciphered copy, the residue of the files are still kept on the disk drive. After the removal, the information about them is removed from the file system, but not from a disk drive. Special apps, 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 a thing unintentionally.
Decrypting the .oohu 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 .oohu files with PhotoRec tool
PhotoRec is an open-source tool, which is designed to recover the deleted or lost files from the disk. It checks each disk sector for the remains of deleted files, and then attempts to recover them. That app is able to recover the files of more than 400 different extensions. 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 Oohu ransomware dangerous?
No. Oohu 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, ransomware creators may publish the rest of the keys when they stop their activity.
✔️Not all of my .oohu 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.