How to unintall Ooss ransomware from a computer?

Also Known As: Ooss virus
Distribution: Moderate
Damage level: Severe

Ooss ransomware removal instructions

What is Ooss?

Ooss belongs to the Djvu ransomware family. It appends the ".ooss" extension to a filename of every encrypted file (e.g., it renames file named "1.jpg" to "1.jpg.ooss", and so on), and creates a text file, a ransom note named "_readme.txt". A ransom note contains details like email addresses of Ooss's developers, price of decryption tool/size of a ransom and other information.

As stated in the "_readme.txt" file, Ooss encrypts documents, photos, databases and other files with the strongest encryption algorithm and unique key. The only way to decrypt files encrypted by Ooos is to use a decryption tool and key that can be purchased from Ooss's developers for $980. Victims can be purchase them for $490 if they will contact cyber criminals in 72 hours after encryption. They can be contacted via or email address. As a proof that Ooos's developers have tools that can decrypt encrypted files they offer a free decryption of one encrypted file. Victims can send them that file via one of the provided email addresses. Typically, cyber criminals behind ransomware (in this case Ooss) are the only ones who have a tool and/or key that can decrypt files encrypted by it. However, not many of them can be trusted. Quite often victims who pay a ransom get scammed (they do not get a decryption tool and/or key). There are no free tools that could be capable of decrypting files encrypted by Ooss, which means the only way to recover files for free (and with no risk of losing money) is to restore them from a backup. It is worthwhile to mention that files remain encrypted even after uninstallation of ransomware, its removal only prevents it from causing further encryptions.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:

Ooss decrypt instructions (_readme.txt)

Ransomware is a type of software that is designed to encrypt victim's data and create (and/or display) a ransom note that contains information on how to contact its developers, size of a ransom and/or other details. Here are examples of other ransomware: Self, Ncov and Blend. Price of a decryption tool and/or key, and cryptographic algorithm (symmetric or asymmetric) that ransomware uses to encrypt data is what usually makes these programs different. Unfortunately, most of the times the only way to decrypt files is to use tools that can be provided only by developers or a particular ransomware. It is possible to decrypt files without their tools only if ransomware has some bugs, flaws, is not fully developed. However, it does not happen often and the only way to recover encrypted files for free to restore them from a backup. That is why it is important to have data backed up and store it on some unplugged storage device or remote server (e.g., Cloud).

How did ransomware infect my computer?

Typically, ransomware and other malicious programs are proliferated through emails/spam campaigns, untrustworthy file and software download sources, fake software updating tools, Trojans and unofficial activation tools. It is very common that cyber criminals spread malware by sending emails that contain malicious attachments (or website links that are designed to download malicious files). Usually they attach files such as Microsoft Office documents, archive files (like ZIP, RAR), PDF documents, executable files (like.exe), and JavaScript files. They seek to deceive recipients into opening a malicious file, that, when opened, installs some malicious software. Examples of unreliable file and software download sources are Peer-to-Peer networks (e.g., torrent clients), free file hosting pages, freeware download websites, unofficial pages, and other similar channels. Quite often cyber criminals use them to host malicious files. They disguise them as harmless, regular and hope that someone will download, and open them. By opening (executing) those files users install malware by themselves. Fake software updating tools cause damage when they install malware instead of updates, fixed, or exploit bugs, flaws of outdated software that is installed on the operating system. Trojan is a type of malicious software that is often designed to cause chain infections/install other software of this kind. However, Trojan can spread malware only if it is installed on a computer. Software 'cracking'/unofficial activation tools supposed to activate licensed programs for free (bypass their activation). However, quite often these tools install malicious software instead.

Threat Summary:
Name Ooss virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .ooss
Ransom Demanding Message readme.txt
Ransom Amount $980/$490
Cyber Criminal Contact,
Detection Names Avast (Win32:CrypterX-gen [Trj]), AVG (Win32:CrypterX-gen [Trj]), Cybereason (Malicious.b276d2), Kaspersky (UDS:DangerousObject.Multi.Generic), Full List Of Detections (VirusTotal)
Symptoms Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files.
Additional Information This malware is designed to show a fake Windows Update window and modify the Windows "hosts" file to prevent users from accessing cyber security websites (more information below).
Distribution methods Infected email attachments (macros), torrent websites, malicious ads, unofficial activation and updating tools.
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.

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How to protect yourself from ransomware infections?

If an email is received from suspicious, unknown address, it is irrelevant and contains some attachment (and/or website link), then should not be trusted. We advise against opening files and links that are included in emails of this kind without being sure that it is safe to open them. Software should be downloaded from official web pages and via direct download links. Peer-to-Peer networks, third party downloaders, unofficial pages, etc., should not be trusted and could be used to proliferate malicious files, programs. Installed software must be updated through implemented functions and/or tools that are designed by official developers. The same applies to its activation. It is worthwhile to mention that it is illegal to activate licensed software with various third party tools, besides, tools of this kind can cause installation of malware. And finally, it is important to regularly scan the operating system for threats with a reputable antivirus or anti-spyware suite, always keep it up-to-date and remove detected threats as soon as possible. If your computer is already infected with Ooss, we recommend running a scan with Spyhunter for Windows to automatically eliminate this ransomware.

Text presented in Ooss ransomware's text file ("_readme.txt"):


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:
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:

Reserve e-mail address to contact us:

Your personal ID:

Screenshot of files encrypted by Ooss (".ooss" extension):

Files encrypted by Ooss ransomware (.ooss extension)

Screenshot of fake Windows update pop-up displayed during the encryption:

Fake Windows pop-up displayed by Ooss during the encryption

IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also add a number of entries to the Windows "hosts" file. The entries contain URLs of various websites, most of which are related to malware removal. This is done to prevent users from accessing malware security websites and seeking help. Our website ( is also on the list. Removing these entries, however, is simple - you can find detailed instructions in this article (note that, although the steps are shown in the Windows 10 environment, the process is virtually identical on all versions of the Microsoft Windows operating system).

Screenshot of websites added to Windows hosts file:

Tro Ransomware adding websites to Windows Hosts file

There are currently two versions of Djvu ransomware infections: old and new. The old versions were designed to encrypt data by using a hard-coded "offline key" whenever the infected machine had no internet connection or the server was timing out/not responding. Therefore, some victims were able to decrypt data using a tool developed by cyber security researcher, Michael Gillespie, however, since the encryption mechanism has been slightly changed (hence the new version, released in August, 2019), the decrypter no longer works and it is not supported anymore. If your data has been encrypted by an older version, you might be able to restore it with the another tool developed by Emsisoft and Michael Gillespie. It supports a total of 148 Djvu's variants and you can find more information, as well as download link and decryption instructions in Emsisoft's official page.

Screenshot of Djvu decryption tool by Emsisoft and Michael Gillespie:

Djvu ransomware decrypter by Michael Gillespie and Emsisoft

Additionally, Emsisoft is now providing a service that allows to decrypt data (again, only if it was encrypted by Djvu variants released before August, 2019) for those victims who have a pair of the same file before and after the encryption. All victims have to do is upload a pair of original and encrypted file to Emsisoft's Djvu decryption page and download the aforementioned decryption tool (the download link will be provided after uploading files). Note that the file processing may take some time so be patient. It is also worth mentioning that the system must have an Internet connection during the entire decryption process, otherwise it will fail.

Screenshot of Emsisoft's Djvu decryption service page:

Djvu ransomware decryption service by Emsisoft

Ooss ransomware removal:

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Spyhunter is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
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Quick menu:

Step 1

Windows XP and Windows 7 users: Start your computer in Safe Mode. Click Start, click Shut Down, click Restart, click OK. During your computer start process, press the F8 key on your keyboard multiple times until you see the Windows Advanced Option menu, and then select Safe Mode with Networking from the list.

Safe Mode with Networking

Video showing how to start Windows 7 in "Safe Mode with Networking":

Windows 8 users: Start Windows 8 is Safe Mode with Networking - Go to Windows 8 Start Screen, type Advanced, in the search results select Settings. Click Advanced startup options, in the opened "General PC Settings" window, select Advanced startup. Click the "Restart now" button. Your computer will now restart into the "Advanced Startup options menu". Click the "Troubleshoot" button, and then click the "Advanced options" button. In the advanced option screen, click "Startup settings". Click the "Restart" button. Your PC will restart into the Startup Settings screen. Press F5 to boot in Safe Mode with Networking.

Windows 8 Safe Mode with networking

Video showing how to start Windows 8 in "Safe Mode with Networking":

Windows 10 users: Click the Windows logo and select the Power icon. In the opened menu click "Restart" while holding "Shift" button on your keyboard. In the "choose an option" window click on the "Troubleshoot", next select "Advanced options". In the advanced options menu select "Startup Settings" and click on the "Restart" button. In the following window you should click the "F5" button on your keyboard. This will restart your operating system in safe mode with networking.

windows 10 safe mode with networking

Video showing how to start Windows 10 in "Safe Mode with Networking":

Step 2

Log in to the account infected with the Ooss virus. Start your Internet browser and download a legitimate anti-spyware program. Update the anti-spyware software and start a full system scan. Remove all entries detected.

If you cannot start your computer in Safe Mode with Networking, try performing a System Restore.

Video showing how to remove ransomware virus using "Safe Mode with Command Prompt" and "System Restore":

1. During your computer start process, press the F8 key on your keyboard multiple times until the Windows Advanced Options menu appears, and then select Safe Mode with Command Prompt from the list and press ENTER.

Boot your computer in Safe Mode with Command Prompt

2. When Command Prompt mode loads, enter the following line: cd restore and press ENTER.

system restore using command prompt type cd restore

3. Next, type this line: rstrui.exe and press ENTER.

system restore using command prompt rstrui.exe

4. In the opened window, click "Next".

restore system files and settings

5. Select one of the available Restore Points and click "Next" (this will restore your computer system to an earlier time and date, prior to the Ooss ransomware virus infiltrating your PC).

select a restore point

6. In the opened window, click "Yes".

run system restore

7. After restoring your computer to a previous date, download and scan your PC with recommended malware removal software to eliminate any remaining Ooss ransomware files.

To restore individual files encrypted by this ransomware, try using Windows Previous Versions feature. This method is only effective if the System Restore function was enabled on an infected operating system. Note that some variants of Ooss are known to remove Shadow Volume Copies of the files, so this method may not work on all computers.

To restore a file, right-click over it, go into Properties, and select the Previous Versions tab. If the relevant file has a Restore Point, select it and click the "Restore" button.

Restoring files encrypted by CryptoDefense

If you cannot start your computer in Safe Mode with Networking (or with Command Prompt), boot your computer using a rescue disk. Some variants of ransomware disable Safe Mode making its removal complicated. For this step, you require access to another computer.

To regain control of the files encrypted by Ooss, you can also try using a program called Shadow Explorer. More information on how to use this program is available here.

shadow explorer screenshot

To protect your computer from file encryption ransomware such as this, use reputable antivirus and anti-spyware programs. As an extra protection method, you can use programs called HitmanPro.Alert and EasySync CryptoMonitor, which artificially implant group policy objects into the registry to block rogue programs such as Ooss ransomware.

Note that Windows 10 Fall Creators Update includes a "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default, this feature automatically protects files stored in the Documents, Pictures, Videos, Music, Favorites, and Desktop folders.

Controll Folder Access

Windows 10 users should install this update to protect their data from ransomware attacks. Here is more information on how to get this update and add an additional protection layer from ransomware infections.

HitmanPro.Alert CryptoGuard - detects encryption of files and neutralises any attempts without need for user-intervention:

hitmanproalert ransomware prevention application

Malwarebytes Anti-Ransomware Beta uses advanced proactive technology that monitors ransomware activity and terminates it immediately - before reaching users' files:

malwarebytes anti-ransomware

  • The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups. More information on online backup solutions and data recovery software Here.

Other tools known to remove Ooss ransomware:

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

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Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

QR Code
Ooss virus QR code
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