Ooss ransomware: what it is and how to remove it
Ooss ransomware is the cryptovirus focused on getting money from people that rely on pirating and illegal activities online. This is yet another Djvu virus version reported by Michael Gillespie that previously offered people help with the decryption tool.
Facts checked October 6, 2026. Removal steps tested on Windows 11 (26H2) and checked against Microsoft's and the browser makers' current documentation. Sections marked as our earlier report are the original text: they describe the threat as it was then and have not been reviewed since. The 2026 status, the removal steps and the questions are current.
Automatic
Get a free scan and check if your PC is infected.
Fortect finds malware, unwanted programs and the Windows damage they leave behind, and repairs it in one pass.
Make sure nothing will rename more files to .ooss: an automatic scan checks the PC first.
Do it yourself · free Remove Ooss ransomware yourself 6 steps, about 18 minutes, no software needed.
Start the steps
Ooss ransomware: summary
| Distribution | The family is known using pirated software and malicious files included in such packaged mostly,[2] but can also infect machines by sending emails with malicious file attachments and links redirecting to malware-laced sites |
|---|---|
| Name | Ooss ransomware |
| Family | STOP virus/ Djvu ransomware |
| File marker | .ooss – the file extension that comes after the original file name and appendix indicating the type of the particular data. Once files get encrypted they become useless and unreadable, so you can see which ones are damaged due to this marker |
| Ransom note | _readme.txt – the file that delivers a message from malicious actors and contains ransom demand, contact information, instructions on how to get cryptocurrency that is their preferred payment method |
| Ransom amount | The amount demanded ranges from $980 and $490 that is the discounted offer for people why contact criminals in the first 72 hours after the ransom note get received |
| Removal | Scan the PC with security software to find and remove the malware and anything installed with it. Fortect scans Windows for malware and repairs the system files and settings it damaged. Remove it nowTo use the full-featured product, you have to purchase a license for Fortect. The scan is free. |
Show 14 more facts
| Danger | This is the threat that focuses on money demands, so when you pay, but your files still remain encrypted, you lose your money and data. Also, instead of recovering your files, criminals can send you additional malware and affect the machine further |
|---|---|
| Detection names | No Microsoft detection name is known |
| Contact | datarestorehelp@firemail.cc, datahelp@iran.ir |
| Encrypted file extension | .ooss |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Damage | Not recorded in the old report |
| Type | File-encrypting ransomware |
| Symptoms | Files renamed with a new extension and a ransom note left in folders |
| Evidence | 5 write-ups by security sites; no sample analysed yet |
| Encrypted files | .ooss |
| Attacker contacts | datarestorehelp@firemail.cc |
| Free decryptor | No free decryptor is known (checked 6 October 2026) |
| First seen | 18 February 2020 |
| Facts checked | 6 October 2026 |
- File extension:
.ooss - Note file:
_readme.txt - Contact:
datarestorehelp@firemail.cc
From our report of Feb 2020 · not reviewed since
More from our earlier report on Ooss ransomware
- Ooss ransomware removal is the process that needs anti-malware tools because ransomware cannot be found manually and you need to thoroughly clean the system to ensure that files will get restored on a safe system
- To get system files and functions affected by the virus repaired, you also need a program.
- Anti-malware tool cannot fix virus damage, so you should rely on system programs like or a PC optimizer that can possibly indicate issues with your settings and OS functions and repair needed files in the registry and so on
How Ooss ransomware behaves
From our report of Feb 2020 · not reviewed since
Ooss ransomware is the version of well-known ransomware that spreads around via pirating services and with the help of infected files
Ooss ransomware is the cryptovirus focused on getting money from people that rely on pirating and illegal activities online.
This is yet another Djvu virus version reported by Michael Gillespie that previously offered people help with the decryption tool. However, the last versions in this family cannot get decrypted with the previously known program, and there are no particular tools that could help all victims. StopDecrypter is no longer helpful because virus creators altered their encryption code and started to use advanced methods in such a file-locking process.
Malicious actors now rely on online keys and IDs, so each victim that suffers from the infection gets a unique ID needed for the recovery and cannot get help from other researchers because of this. Until August 2019, people got help from malware experts when offline keys got used to recover many files all over the world.
Ooss ransomware virus is the version that can permanently damage your files because there are not many other options. Even though, Emsisoft released a decryptor for Djvu, the software works for victims that have the variant using offline keys. Typically, such victims' ID ends in t1, so you can easily identify that.
However, right now there are little to none samples that use offline IDs for encryption. When your files get marked using .ooss file appendix, you can be sure that there is a cryptovirus on your device, so get a proper anti-malware tool and make sure to clean the traces of this malware, so it can be terminated and files restored on the clean and safe machine.
Ooss ransomware belongs to the family of malware that hasn't altered the ransom note file for years now. _readme.txt file delivers the same message and is named the same for most of the time that the Djvu family is observed. The message gets slightly changed because contact emails differ from version to version. However, the same contact emails get displayed for at least three or four versions at the time.
The ransom note added on the desktop after OOSS ransomware encryption:
However, no one ensures that after the email, Ooss ransomware developers going to send you that decryption software or a key needed for file restoring. You shouldn't consider paying or contacting these criminals at all because they cannot guarantee that. In most cases, even big targets, companies that get affected by such ransomware decide not to pay and recover their networks themselves without risking again.
Experts always recommend recovering files with your backups after the Ooss ransomware removal instead of paying these hackers because secondary encryption can permanently affect your photos, videos, documents, and other common files. Despite the file-locking process, this family can possibly load additional malware like info-stealing trojans and more dangerous threats.
You should consider that and make sure to remove Ooss ransomware as soon as you possibly can, use anti-malware program for the job because such tools are designed to detect threats like ransomware and trojans, malware created to spread another virus around. This is not a tool or program that could be found and uninstalled.
The same goes for Ooss ransomware virus damage that cannot be indicated by the AV tools even. Anti-malware programs cannot recover your files, or fix system damage, so go for a system optimization tool a cleaner, something like and ensure that the machine is checked yet again. This way, you can repair needed files in system folders and recover default settings of the startup, registry entries.
File locking process that Ooss ransomware first runs on the infected system relies on army-grade encryption algorithms that allow threats to change the original code of a file, so it cannot be used again and becomes unopenable. There are many algorithms and methods that can be used in such procedures, so the latest changes and improvements made by malicious actors caused huge differences in the persistent and decryption possibilities.
Previously other versions before Ooss ransomware were decryptable, and new versions each week were not that scary since many victims got their files repaired thanks for the offline keys and some researchers. When cybercriminals use offline IDs nowadays, victims can also get their files restored since one obtained key can restore the same type of data for many other devices.
When the connection to malicious hacker-hosted C&C server is not made, Ooss ransomware relies on offline ID, and these ones get changed with each virus variant - extension. Everyone who has their files encrypted by the save version has the same ID and can help others to get their data back.
However, the summer of 2019 ended with significant changes in the RSA encryption method used by these criminals Ooss ransomware. Online keys get used for pretty much each new release, and virus connects to the command and control servers to get randomly generated victim ID that is unique for each victim.
In such cases, the only way to get files recovered is a proper decryption tool that relies on the same technique as the encryption that was launched in the first stage of the ransomware attack. Unfortunately, for this version you have the only solution - restore files using data backups.
From our report of Feb 2020 · not reviewed since
Malware identification flaws help spread ransomware payload files online
There are many ways that criminals use for delivering their shady programs and when it comes to such malicious programs like crypto-malware, it is extremely uncommon to even notice the infection.
When malicious script with ransomware payload is injected on the file that gets attached to email notifications the encryption starts immediately after opening the infected document or visiting the link. It happens due to malicious macro viruses that get triggered by the user why receives the scammy message.
However, this particular family is known for using another flaw of online users to their advantage - paying less attention to details and relying on illegal activities like pirating and torrent service. When the person downloads the license key for original software or cheatcodes of video games malicious files including ransomware dropper or virus that infects the system with cryptovirus directly get loaded.
Choosing legitimate sources for programs and avoiding torrent sites, pirating services, shady sites, and other illegal activities can help avoid these infections. Also, clean the email box more often, be more suspicious, remove received emails that raise questions.
The Ooss ransomware note
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-7YSRbcuaMa
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:
datarestorehelp@firemail.cc
Reserve e-mail address to contact us:
datahelp@iran.ir
Your personal ID:
How to remove Ooss ransomware
Tools you'll need
All of these are free except where noted. Download them on a clean device if the infected PC is offline.
- A USB stick: to keep the ransom note, two or three encrypted files and screenshots off the infected PC.
- Microsoft Defender Offline: built into Windows 11 and Windows 10; scans before Windows starts, so running malware cannot hide.
- Microsoft Safety Scanner: a second, portable scanner with current signatures; each download works for 10 days.
- ID Ransomware: identifies the family from the note and one encrypted file and says whether a decryptor exists.
- No More Ransom: the free decryptors from police and security companies; check it again every few months.
- Fortect (optional): scans Windows for malware and repairs the system files and settings it damaged. The free scan is in the box above.
How to remove Ooss ransomware and get your files back
Work in this order.
Disconnecting comes first, removal comes before any restore, and nothing here asks you to contact the attackers.
Step 1: Disconnect the PC and unplug backup drives
Unplug the network cable or turn off Wi-Fi, and disconnect USB drives, external disks and network shares, so Ooss ransomware cannot reach more files. Pause OneDrive, Google Drive or Dropbox sync, because synced folders upload the encrypted copies over the good ones.
Leave the PC on but offline while you read the next steps, since a restart can let the ransomware run again. This applies to Windows 11 and Windows 10 alike.
Windows 11: turn off Wi-Fi to take the PC offline. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 2: Save the ransom note and confirm the family
Your files now end in
.oossand the instructions are in_readme.txt. Save both to a USB stick, a copy of the note and two small encrypted files, before anything else.On another device, check them with ID Ransomware or Crypto Sheriff: the family name decides which decryptor, if any, can help. Keep the note's ID and contact line for your report.
Windows 11: the ransom note and encrypted files to copy for identification. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 3: Check for a free decryptor
Our last check found that for Ooss ransomware, no free decryptor is known (checked 6 October 2026). Look again yourself in the No More Ransom list and the free decryptor pages of Emsisoft, Avast and Kaspersky, which add new families every year.
A decryptor needs the ransomware gone first, or it encrypts the files again. Keep at least one copy of the encrypted files on an external drive, even if no tool works yet.
Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 4: Remove the ransomware before you restore or decrypt
Removing Ooss ransomware does not bring the files back, but it has to come first. Start with Defender's Full scan, then the offline scan from the same Scan options page, which checks the disk before Windows loads.
If the scan cannot start, use Safe Mode with Networking. Delete the ransom notes only after you have saved a copy, because removal tools sometimes leave them behind on Windows 11 and Windows 10.
Windows 11: Windows Security > Virus & threat protection > Scan options. Full procedure with screenshots: Run a Microsoft Defender Offline scan
Step 5: Look for shadow copies of the files
Windows keeps shadow copies for restore points and backups, and some ransomware fails to delete them.
vssadmin list shadowsin an administrator Command Prompt tells you at once whether any exist.If they do, right-click the folder that held your files, open Properties > Previous Versions, select a version from before the attack, and click Open to check it before you Restore or copy the files out. Windows 11 and Windows 10 both have the tab.
Windows 11: vssadmin list shadows shows whether shadow copies exist. Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 6: Restore the files from a backup or recover deleted originals
A backup made before the attack is the surest way back. Connect it only once the PC is clean, then restore from File History, Windows Backup, OneDrive's Restore your OneDrive or your own external copies.
Without a backup, try file recovery: the originals that Ooss ransomware deleted may still be on the disk until something overwrites them. Install nothing new on the drive you want to recover from on the Windows 11 or Windows 10 PC.
Full procedure with screenshots: Recover deleted files (Recycle Bin, backups, OneDrive) On uGetFix
Instructions for each browser and system
The detailed steps for every browser and system this guide covers. Open the one you use.
Manual removal using Safe Mode
Important! →
Manual removal guide might be too complicated for regular computer users. It requires advanced IT knowledge to be performed correctly (if vital system files are removed or damaged, it might result in full Windows compromise), and it also might take hours to complete. Therefore, we highly advise using the automatic method provided above instead.
Step 1. Access Safe Mode with Networking
Manual malware removal should be best performed in the Safe Mode environment.
Windows 7 / Vista / XP
- Click Start > Shutdown > Restart > OK.
- When your computer becomes active, start pressing F8 button (if that does not work, try F2, F12, Del, etc. - it all depends on your motherboard model) multiple times until you see the Advanced Boot Options window.
- Select Safe Mode with Networking from the list.
Windows 10 / Windows 8
- Right-click on Start button and select Settings.
- Scroll down to pick Update & Security.
- On the left side of the window, pick Recovery.
- Now scroll down to find Advanced Startup section.
- Click Restart now.
- Select Troubleshoot.
- Go to Advanced options.
- Select Startup Settings.
- Press Restart.
- Now press 5 or click 5) Enable Safe Mode with Networking.
Step 2. Shut down suspicious processes
Windows Task Manager is a useful tool that shows all the processes running in the background. If malware is running a process, you need to shut it down:
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Click on More details.
- Scroll down to Background processes section, and look for anything suspicious.
- Right-click and select Open file location.
- Go back to the process, right-click and pick End Task.
- Delete the contents of the malicious folder.
Step 3. Check program Startup
- Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
- Go to Startup tab.
- Right-click on the suspicious program and pick Disable.
Step 4. Delete virus files
Malware-related files can be found in various places within your computer. Here are instructions that could help you find them:
- Type in Disk Cleanup in Windows search and press Enter.
- Select the drive you want to clean (C: is your main drive by default and is likely to be the one that has malicious files in).
- Scroll through the Files to delete list and select the following:
Temporary Internet Files
Downloads
Recycle Bin
Temporary files - Pick Clean up system files.
- You can also look for other malicious files hidden in the following folders (type these entries in Windows Search and press Enter):
%AppData%
%LocalAppData%
%ProgramData%
%WinDir%
After you are finished, reboot the PC in normal mode.
From our report of Feb 2020 · not reviewed since
Get rid of the .ooss files virus completely with AV tools
Make the system malware-free again and terminate the Ooss ransomware virus with anti-malware tools because such software can help eliminate anything related to the intruder and additional threats that may run in the background without your knowledge. Tools designed to scan the machine fully can check many hidden places.
Ooss ransomware removal gives the best results for you when you use proper tools like , or . These are security programs that can find, detect, and remove the ransomware and other possibly dangerous intruders that you cannot notice yourself. These programs are not the ones that could recover encrypted files, but you need to terminate the virus to have a totally secure machine.
When you remove Ooss ransomware using anti-malware tools, professional software can eliminate traces and potentially harmful parts of the threat. However, after that, you still need to repair damage made in system folders with tools like , and only then worry about data recovery. When you double-check and ensure that the system is clear, rely on your data backups or third-party software, and restore encrypted data.
[GI=method-1]Reboot the machine in Safe Mode and get rid of the Ooss ransomware by scanning the system with AV tool
[GI=method-2]System Restore feature should help with virus termination because this function can recover the system in a previous stage when malware was not running
Windows Previous Versions feature restores data individually
When System Restore is enabled, you can rely on Windows Previous Versions feature for your encrypted files
ShadowExplorer is the method helpful for Ooss ransomware encrypted files
Shadow Volume Copies should be left untouched if you want to use this method for your encrypted files
Particular decryption tool for Ooss ransomware is not developed, but DJVU decryptor may help
Try this decryption tool designed for Djvu versions using offline IDs
Report it and recover your files
Report it
Report the attack even if you do not expect the files back: insurers and banks ask for the report number, and police use the contacts in the note to link cases.
- United States
- FBI IC3 · FTC ReportFraud
- United Kingdom
- Report Fraud (formerly Action Fraud) · NCSC
- Australia
- ReportCyber (ASD)
- EU countries
- Europol: national reporting sites
Give the victim ID, the note and the date the files were encrypted. A business that holds personal data may also have to notify its data protection authority, in the EU within 72 hours.
Protect the files you restore
Restore only after the scans are clean and the PC no longer shows files that end in .ooss and no longer open; otherwise the restored copies can be damaged again.
Then build a backup that survives the next infection:
- one copy in the cloud with version history
- one on an external drive that is disconnected between backups
- the working copy on the PC
Version history matters because a backup that syncs damaged files overwrites the good ones.
How to do this with the tools built into Windows: the 3-2-1 backup rule on Windows.
Do not let government spy on you
The government has many issues in regards to tracking users' data and spying on citizens, so you should take this into consideration and learn more about shady information gathering practices.
Avoid any unwanted government tracking or spying by going totally anonymous on the internet.
You can choose a different location when you go online and access any material you want without particular content restrictions. You can easily enjoy internet connection without any risks of being hacked by using VPN.
Control the information that can be accessed by government any other unwanted party and surf online without being spied on. Even if you are not involved in illegal activities or trust your selection of services, platforms, be suspicious for your own security and take precautionary measures by using the VPN service.
Backup files for the later use, in case of the malware attack
Computer users can suffer from data losses due to cyber infections or their own faulty doings.
Ransomware can encrypt and hold files hostage, while unforeseen power cuts might cause a loss of important documents. If you have proper up-to-date backups, you can easily recover after such an incident and get back to work. It is also equally important to update backups on a regular basis so that the newest information remains intact - you can set this process to be performed automatically.
When you have the previous version of every important document or project you can avoid frustration and breakdowns. It comes in handy when malware strikes out of nowhere. Use for the data restoration process.
Questions about Ooss ransomware
How do I open .ooss files?
You cannot open them by renaming or with another program, because the content of files ending in .ooss has been encrypted. The only ways back are a working decryptor for the family, or clean copies from elsewhere:
- OneDrive versions
- File History
- an offline backup drive
- Previous Versions if the ransomware did not delete them
Identify the family first by uploading the ransom note and one encrypted file to ID Ransomware or No More Ransom. Avoid websites and programs that promise to open any encrypted file; they do not work and some are scams.
Should I pay the ransom in _readme.txt?
Not before you have tried everything else. Identify the family from _readme.txt and one encrypted file, check No More Ransom for a free decryptor, and look for clean copies in OneDrive, backups and Previous Versions.
Paying funds further attacks, may be illegal if the group is sanctioned, and is no promise of a working key: many victims get partial or broken decryption. If you consider paying for business-critical data, involve the police and a professional incident responder first, and never pay through intermediaries who promise their own decryption.
Is there a free Ooss ransomware decryptor?
We last checked on 6 October 2026, and for Ooss ransomware no free decryptor is known. We check No More Ransom, which collects free tools from police and security companies, and the decryptor pages of the major antivirus vendors. A working decryptor exists only when the encryption has a flaw or the keys were leaked or seized.
Ignore sites and videos that offer a "Ooss ransomware decryptor" for download or for a fee: these are usually scams or malware. Real decryptors are free and come from known security companies or law enforcement. Keep the encrypted files in case a tool appears later.
Are ransomware recovery services legitimate?
Some are, but read the offer carefully. Genuine data-recovery firms recover deleted originals from disks or rebuild damaged files, and they say so. Others promise to "decrypt any ransomware" for a fixed price, which is impossible without the key; they quietly pay the attackers and keep a margin, sometimes without telling the victim.
Be especially careful with services that contact you after you post about the attack online. Ask for references, a written method and a no-result-no-fee clause, and check the free tools on No More Ransom first.
How did Ooss ransomware get on my computer?
The way Ooss ransomware spreads has not been documented yet, so look at your own recent activity. On home PCs, ransomware most often comes with cracked programs, game cheats, key generators and fake updates, or with an e-mail attachment that was opened. On business networks, attackers usually log in through Remote Desktop with a stolen or guessed password.
Think back to what was downloaded or installed in the days before files that end in .ooss and no longer open, and check the Downloads folder and Installed apps sorted by date. Keep anything suspicious for your report, but do not run it again.
Did Ooss ransomware steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Ooss ransomware, but the only confirmed sign is files that end in .ooss and no longer open, which says nothing about what happened before. Many current ransomware attacks copy files or run a password stealer first, so it is wise to act as if they did.
From a clean device, change the passwords that were saved in the browsers on this PC, starting with e-mail and banking, sign out of all sessions and turn on two-step verification. Watch bank statements and account activity for the next few weeks.
Is Ooss ransomware the same as other ransomware with a similar name?
Not necessarily. Ransomware names come from the file extension, the note or a word in the code, so unrelated families often end up with similar names, and one family can appear under several names. The difference matters: a decryptor or advice for one family does not fit another and can damage files.
Compare the ending added to your files and the exact name of the note with the summary table at the top of this guide, then upload the note and one encrypted file to ID Ransomware from a clean device. If the result names another family, follow the guide for that family instead.
What does _readme.txt tell me about the ransomware?
Quite a lot. The file name _readme.txt, the wording, the contact addresses and the format of the personal ID are typical for each family. Uploading the note together with one encrypted file to ID Ransomware or No More Ransom's Crypto Sheriff usually names the family within seconds.
That name decides your options: some families have free decryptors, some can be partially recovered, and some cannot be decrypted at all. The note's claims about stolen data should be taken seriously but not at face value.
My files got .ooss overnight. What happened?
Ransomware often runs at night or when the PC is idle, so the encryption finishes before anyone notices. It usually entered earlier through a cracked program, a fake installer, an e-mail attachment or remote desktop with a weak password.
The .ooss extension marks every file it reached. Start by disconnecting the PC from the network, then identify the family from the ransom note and one encrypted file, check for a decryptor, and look for copies in backups and OneDrive before you consider anything else.
Will Fortect remove Ooss ransomware?
Fortect scans Windows for malware and unwanted programs and repairs the system files and settings they change, and its free scan shows what it finds on your PC before you decide anything.
For Ooss ransomware, follow the plan above as well: the browser steps take back permissions and settings that no scanner treats as a threat, and uninstalling the program that brought it removes the source.
Run Microsoft Defender's full scan and, if anything was found, its offline scan as a second opinion. If the symptoms are gone after the plan and both scans are clean, there is nothing more to do.
Sources
- Twitter: .ooss v208 report (read October 6, 2026)
- Cyware: Cracked software versions are harboring Djvu Ransomware (read October 6, 2026)
- CSOonline: To pay or not pay a hacker's ransomware demand? It comes down to cyber hygiene (read October 6, 2026)
- CISA: StopRansomware (read October 6, 2026)
- No More Ransom (read October 6, 2026)