URSA ransomware, Ursa 1.0: what it is and how to remove it
URSA ransomware is a type of computer virus that focuses on money extortion. Unlike many other threats of a similar kind, it does not append any extension to personal files, although it does use the encryption algorithm (RSA-2048) for the purpose.
Facts checked October 7, 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.
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URSA ransomware, Ursa 1.0: summary
| Name | URSA ransomware, Ursa 1.0 |
|---|---|
| Type | Ransomware, data locking malware, cryptovirus |
| Encryption method | RSA-2048 |
| File extension | The virus does not append any extensions, although files are still encrypted and cannot be opened |
| Ransom note | RECOVER_YOUR_FILES.HTML and RECOVER_YOUR_FILES.TXT; the text is quoted in full below |
| Contact | No email is provided, although the attackers ask to access a special page on the Tor web browser |
| 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 12 more facts
| Bitcoin wallet | Cybercriminals provide a Bitcoin wallet that the $350 ransom should be transferred to – [payment address omitted] |
|---|---|
| File Recovery | If no backups are available, recovering data is almost impossible. Nonetheless, we suggest you try the alternative methods that could help you in some cases – we list them below |
| Detection names | No Microsoft detection name is known |
| Encrypted file extension | Not recorded in our earlier report |
| Decryptor | No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates |
| Distribution | Not recorded in the old report |
| Damage | Not recorded in the old report |
| Symptoms | A ransom note left in folders |
| Evidence | 4 write-ups by security sites; details still limited |
| Free decryptor | No free decryptor is known (checked 7 October 2026) |
| First seen | 28 January 2021 |
| Facts checked | 7 October 2026 |
- Note file:
RECOVER_YOUR_FILES.HTML
From our report of Jan 2021 · not reviewed since
More from our earlier report on URSA ransomware, Ursa 1.0
- Perform a full system scan with powerful security software, such as
- Malware can seriously tamper with Windows systems, causing errors, crashes, lag, and other stability issues after it is terminated.
How URSA ransomware, Ursa 1.0 behaves
From our report of Jan 2021 · not reviewed since
URSA ransomware is a data-locker that does not rename encrypted files
URSA ransomware is a type of computer virus that focuses on money extortion.
Unlike many other threats of a similar kind, it does not append any extension to personal files, although it does use the encryption algorithm (RSA-2048) for the purpose. As a result, you will not be able to open any of the pictures, videos, documents, or other files without decryption software that is only be provided by hackers behind the malware.
There are two ransom notes that the URSA virus drops as soon as it finishes to lock files - RECOVER_YOUR_FILES.HTML and RECOVER_YOUR_FILES.TXT. In these files, attackers explain what happened to victims' data and ask them to download the Tor browser. This would provide access to a specially-crafted webpage with extensive instructions on how to buy Bitcoins and pay $350 for a decryptor.
There is a lot of ransomware around. While established strains are going steady with several variants being released weekly (for example, Djvu actors released Pola and Wbxd in one week alone), new ones are emerging as well. Ursa 1.0 is one of them, and it seems like these hackers are not playing games.
This virus has several features that we do not see that often overall - they include:
While there are no extensions present, the files are still encrypted, and you will not be able to open them. As hackers explain within the ransom note, you need a private key that is only available to the attackers.
Unfortunately, there are no 100% effective methods that would replace the keys provided by malware authors - the only secure way to restore data is by using backups that should have been created before the attack happened.
One of the first things you might see after the infection is the following ransom note:
As you can see, Ursa 1.0 virus authors do a good job at explaining to victims what to do next - it is in their best interest to do so in order to get the payment of 0.0086 BTC. On the specially crafted Tor page, the attackers also state that users only have one week to provide payment for the URSA decryptor; otherwise, the files will be lost forever.
Threatening with permanent data loss is a common tactic among ransomware authors and was especially popular previously. The time limit is there to intimidate victims and make them pay quicker. Despite this, there is no proof or guarantee that hackers will indeed provide the decryption tool after payment, and if they will delete the private key after a week.
Therefore, if you decide to pay, you risk not only your files but also your money, hence security experts advise against it. Instead, you can rely on alternative methods that might help you, although keep in mind that you need to remove Ursa ransomware before applying them. Also, making encrypted file backups on a separate medium (such as a USB flash drive) is recommended.
Ursa virus removal can be performed with a variety of security tools - such as . can fix the Windows registry, replace damaged system files with new ones and prevent crashes, errors, and other stability issues after the virus is eliminated.
- It does not append any file extensions
- It does not provide contact email and relies on Tor instead
- Uses carefully crafted ransom notes.
From our report of Jan 2021 · not reviewed since
Malicious actors use several methods for malware distribution
If you are wondering how you got infected with malware, it is likely to be due to actions that are considered risky.
Typically, cybercriminals distribute malware in several ways in order to make the infection rate, along with payment possibilities, much higher. Here are a few methods that are worth mentioning:
Therefore, in order to avoid the treacherous ransomware infection in the future, we highly recommend you practice caution when using a computer connected to the internet. While employing a robust security tool can prevent most of the infections, disabling it manually to download a software crack could still end up badly.
Stay away from email attachments that ask you to enable macro function, patch all the software on your computer, use strong passwords for all your accounts (and never reuse them!), and never disable your security software to install a pirated game or software crack.
- Repacked installers for various software, such as Adobe Reader
- Software cracks, loaders or keygens
- Malicious spam email attachments and hyperlinks
- Software vulnerabilities and drive-by downloads
- Fake updates, etc.
The URSA ransomware, Ursa 1.0 ransom note
All your files have been encrypted with URSA 1.0
* What happend to your files?
All of your files were protected by a strong encryption with RSA-2048 using Ursa 1.0
More information about the encryption keys using RSA-2048 can be found here: hxxps://en.wikipedia.org/wiki/RSA_(cryptosystem)
* What does this mean?
This means that the structure and data within your files have been irrevocably changed,
you will not be able to work with them, read them or see them, it is the same thing as losing them forever, but with our help, your can restore them.
* How did this happen?
Especially for you, on our server was generated the secret key pair RSA-2048 public and private.
All your files were encrypted with the public key, which has been transferred to your computer via the internet. Decrypting of your files is only possible with the help of the private key and decrypt program, which is on our secret server.
* What do i do?
Alas, if you do not take the necessary measures for the specified time then the conditions for obtaining the private key will be changed.
If you really value your data. then we suggest you go directly to your personal page. Do not waste valuable time searching for other solutions, because they do not exist.
Important information.
Your Personal Page:
1. Download and install tor-browser hxxps://www.torproject.org/download
2. After a successful installation, run the browser and wait for initialization.
3. Type or copy your personal page that you see above, into the address bar.
4. Follow the instructions on your personal page.
How to remove URSA ransomware, Ursa 1.0
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 URSA ransomware, Ursa 1.0 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
URSA ransomware, Ursa 1.0 encrypts everything it can reach, including drives and shares you connect later. Cut the network first: cable out, or Wi-Fi off from the taskbar.
Then unplug every USB stick and backup disk and pause cloud sync, so the encrypted versions do not replace your online copies. Do not reconnect any of them until the ransomware is removed from the Windows 11 or Windows 10 PC.
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 identify the family
Find the ransom note, usually a
.txt,.htmlor .hta file in every folder or on the desktop, and copy it with one or two encrypted files to a USB stick.From another device, upload them to ID Ransomware or No More Ransom's Crypto Sheriff, which name the family from the note and the file extension. Write down the contact address and your personal ID from the note for the report.
Warning: Never contact the attackers from the infected Windows 11 or Windows 10 PC.
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
For URSA ransomware, Ursa 1.0, no free decryptor is known (checked 7 October 2026). Search the family name in the No More Ransom decryption tools list and in the free decryptors of Emsisoft, Avast and Kaspersky, because new tools appear years after an attack.
Important: Keep the encrypted files even if nothing works today, and do not pay before every free option is ruled out: payment does not guarantee a working key.
Decryptors run on Windows 11 and Windows 10, but only after the ransomware itself is removed.
Full procedure with screenshots: Ransomware: first steps, finding a decryptor and recovering files
Step 4: Remove the ransomware before you restore or decrypt
Restoring or decrypting files while URSA ransomware, Ursa 1.0 still runs lets it encrypt them again. Run a Full scan in Windows Security > Virus & threat protection > Scan options, then the Microsoft Defender Antivirus (offline scan).
If the ransomware blocks Windows Security, start Safe Mode with Networking and scan from there. Some families install a password stealer as well, so let both scans finish on Windows 11 or 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
Open Command Prompt as administrator and run
vssadmin list shadows. If it lists copies dated before the attack, right-click a folder with encrypted files in File Explorer, choose Properties > Previous Versions, and open or restore a version from before that date.ShadowExplorer, a free tool, shows the same copies when the tab is empty or hidden. Most current families delete shadow copies, so an empty list is normal, but the check takes two minutes on Windows 11 or Windows 10.
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
Restore from an external backup, File History or OneDrive's version history, choosing a date before the attack. Connect the backup drive only after the scans are clean, or the ransomware encrypts it too.
If there is no backup, file recovery software can sometimes find the deleted originals, because some ransomware writes an encrypted copy and deletes the original file.
Stop writing to the drive and try recovery on Windows 11 or Windows 10 before new files overwrite the space.
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 Jan 2021 · not reviewed since
Ursa 1.0 removal and file recovery options
As we already mentioned, there is no reliable way to restore the encrypted files without acquiring the decryption key from cybercriminals.
Because it is also unique, you won't get away with contacting other victims and applying it to your files - this is one of the reasons why ransomware is so effective when it comes to extortion.
Paying criminals could be a waste of money, as they are not obligated to send you a decryptor (even if they might say so initially). Thus, rather focus on Ursa ransomware removal and alternative file recovery methods.
While you technically can remove Ursa virus manually, it requires superior computer skills. Thus, we advise you to stick to a more reliable method that would find and delete malware automatically - perform a full system scan with or security applications.
After elimination, you could use that would restore damaged system files and prevent crashes or errors due to the malware attack. Finally, you should try using alternative data recovery methods instead of paying the attackers - we provide them below.
[GI=method-1]Use Safe Mode with Networking if malware is tampering with your security software:
Data recovery software might sometimes be useful when trying to restore files encrypted by ransomware.
Windows Previous Versions feature might be a solution for you
You might be able to restore files one-by-one when using Windows Previous Versions.
ShadowExplorer might be help you need
If Ursa 1.0 failed to delete Shadow Copies, this tool should be able to retrieve all the encrypted files.
No decryptor is currently available
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.
Backups: the 3-2-1 rule
Keep three copies of files that matter, on two kinds of storage, with one copy offline or off-site.
A disk that stays plugged in is reached by malware like URSA ransomware, Ursa 1.0 together with the PC; one you connect only for the backup is not.
On Windows 11, File History keeps versions on an external drive, and OneDrive keeps earlier versions of synced files. Before restoring anything, make sure the PC no longer shows ransom notes called RECOVER_YOUR_FILES.HTML in every folder.
Setting it up step by step: 3-2-1 backups on Windows 11 and 10.
Stream videos without limitations, no matter where you are
There are multiple parties that could find out almost anything about you by checking your online activity.
While this is highly unlikely, advertisers and tech companies are constantly tracking you online. The first step to privacy should be a secure browser that focuses on tracker reduction to a minimum.
Even if you employ a secure browser, you will not be able to access websites that are restricted due to local government laws or other reasons. In other words, you may not be able to stream Disney+ or US-based Netflix in some countries. To bypass these restrictions, you can employ a powerful VPN, which provides dedicated servers for torrenting and streaming, not slowing you down in the process.
Data backups are important - recover your lost files
Ransomware is one of the biggest threats to personal data.
Once it is executed on a machine, it launches a sophisticated encryption algorithm that locks all your files, although it does not destroy them. The most common misconception is that anti-malware software can return files to their previous states. This is not true, however, and data remains locked after the malicious payload is deleted.
While regular data backups are the only secure method to recover your files after a ransomware attack, tools such as can also be effective and restore at least some of your lost data.
Questions about URSA ransomware, Ursa 1.0
When will a decryptor for URSA ransomware, Ursa 1.0 be released?
Nobody can promise a date. When we last checked, on 7 October 2026, no free decryptor is known. Decryptors usually appear after one of three events:
- police seize the attackers' servers and keys
- the authors leak or publish the master keys
- researchers find a mistake in how the ransomware generates keys
Some families got a tool within weeks, others never. Keep the encrypted files and the note on an external drive, check No More Ransom every few months, and follow news about the URSA ransomware, Ursa 1.0 family. A decryptor may need an original file, so keep any unencrypted copies too.
Did URSA ransomware, Ursa 1.0 steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by URSA ransomware, Ursa 1.0, but the only confirmed sign is ransom notes called RECOVER_YOUR_FILES.HTML in every folder, 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.
Should I pay the ransom?
We advise against it, and so do the FBI, Europol and national cyber agencies. Payment does not guarantee a working tool: some attackers never reply, some tools damage files, and some variants have no decryptor at all. Paying also funds further attacks and can make you a target again.
Before considering payment, try every recovery option in this guide and report the attack. Companies must involve their legal adviser and insurer, because payments to sanctioned groups can be illegal. If files are truly irreplaceable, store the encrypted copies and wait; decryptors sometimes appear later.
Can a data-recovery company decrypt my files for a fee?
Only if a decryptor already exists or the company pays the attackers for you. Some "ransomware recovery" services advertise that they can decrypt families with no known flaw; in practice they negotiate with the attackers and add their own fee. Others use the same free tools listed on No More Ransom.
Before you hire anyone, ask in writing how they will recover the files, whether they will contact the attackers and what happens if they fail. A legitimate service answers clearly. If a free decryptor exists for your family, you can run it yourself.
How did URSA ransomware, Ursa 1.0 get on my computer?
The way URSA ransomware, Ursa 1.0 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 ransom notes called RECOVER_YOUR_FILES.HTML in every folder, and check the Downloads folder and Installed apps sorted by date. Keep anything suspicious for your report, but do not run it again.
Is URSA ransomware, Ursa 1.0 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.
Should I open RECOVER_YOUR_FILES.HTML?
Reading it is fine if you open it in Notepad. A plain text RECOVER_YOUR_FILES.HTML cannot harm the PC. Be careful with notes in HTA or HTML format: double-clicking those runs them in a window that can contain scripts, so right-click and choose Open with > Notepad instead.
The note tells you the contact addresses, the claimed amount and the deadline. Do not visit links or write to the addresses from this PC. Use the note to identify the family and check for a free decryptor first.
Can I get my files back without paying after RECOVER_YOUR_FILES.HTML appeared?
Sometimes. Free decryptors exist for a number of families, especially older ones or those with flaws in their encryption. Other routes are copies the ransomware missed:
- OneDrive version history
- File History
- a backup drive that was disconnected
- email attachments
- phone photos
Shadow copies are often deleted, but it is worth checking. Identify the family from RECOVER_YOUR_FILES.HTML first, because that tells you which of these routes is realistic. Keep encrypted files even if nothing works now; decryptors are sometimes released months later.
How do I open my .docx, .jpg and other files locked by URSA?
You cannot open locked files normally while they stay encrypted, and renaming them will not help. Our earlier report did not record the extension that URSA adds, so check one locked file name and the ransom note for it.
No free decryptor is known for this variant; check No More Ransom (nomoreransom.org) for updates. Do not rename the files, change the extension or edit them, because that can make recovery harder. Copy the locked files to an external drive before you clean the system, so a decryptor released later still has them.
Will Fortect remove URSA ransomware, Ursa 1.0?
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 URSA ransomware, Ursa 1.0, 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
- CompariTech: What is RSA encryption and how does it work? (read October 7, 2026)
- Wikipedia: Vulnerability (computing) (read October 7, 2026)
- CISA: StopRansomware (read October 7, 2026)
- No More Ransom (read October 7, 2026)
- FTC: How to recognize, remove and avoid malware (read October 7, 2026)