Btos ransomware: what it is and how to remove it
Btos ransomware is a cryptovirus that makes users scared and frustrated when commonly used data becomes useless after the encryption process. This threat comes silently and victims cannot fully understand what happened until the ransom note file _readme.txt gets placed on the desktop and in other folders with affected files.
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.
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 the ransomware behind _readme.txt is gone before you plug in backups: a scan helps check.
Do it yourself · free Remove Btos ransomware yourself 6 steps, about 18 minutes, no software needed.
Start the steps
Btos ransomware: summary
| Name | Btos ransomware |
|---|---|
| Family | Djvu virus |
| Main symptoms | The malware encrypts common files and makes them unreadable, so people get encouraged to pay the amount demanded in the ransom note that gets placed on the system after successful file-locking. The payment is asked in cryptocurrency and criminals claim that once the money gets transferred the victim can receive the decryption key needed to recover encoded files |
| File marker | .btos appears after the original file type indicating extension when the original code of the document, image, audio, video file gets altered |
| Contact emails | helpmanager@firemail.cc or helpmanager@iran.ir |
| Ransom note | _readme.txt; the text is quoted in full below |
| 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 13 more facts
| Danger | Paying can lead to permanent data and money loss if you decide to transfer the asked amount to the account belonging to criminals. Malware involves blackmailing and criminals may try to get more money from you when you contact them directly or send more severe malware directly |
|---|---|
| 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 |
| Type | File-encrypting ransomware |
| Symptoms | A ransom note left in folders |
| Evidence | 4 write-ups by security sites; details still limited |
| Attacker contacts | helpmanager@firemail.cc |
| Free decryptor | No free decryptor is known (checked 7 October 2026) |
| First seen | 30 January 2020 |
| Facts checked | 7 October 2026 |
- Note file:
_readme.txt - Contact:
helpmanager@firemail.cc
From our report of Jan 2020 · not reviewed since
More from our earlier report on Btos ransomware
- _readme.txt - a document that contains the message from virus developers and instructions on getting Bitcoins, transferring the payment to criminals.
- This is the file that shows particular contact emails for virus creators and the ransom amount of $980
- Btos ransomware removal requires professional anti-malware tools because this is the best way to clean the machine fully from all the possible trojans and associated files that can be installed behind your back
- Ransomware displays a few symptoms but can run more malicious activities in the background and affect various settings without your knowledge.
- To fix such damage you should use or a similar system application.
- This is how your registry gets repaired without causing additional damage
The Btos 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-Oc0xgfzC7q
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:
helpmanager@firemail.cc
Reserve e-mail address to contact us:
helpmanager@iran.ir
Your personal ID:
How to remove Btos 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 Btos 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 Btos 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 identify the family
The name of the family decides whether a free decryptor can help. Copy the ransom note and two small encrypted files to a USB stick, and check them on another device with ID Ransomware or Crypto Sheriff.
Note the extension added to the files, the contact address and the victim ID shown in the note. Keep the originals on the Windows 11 or Windows 10 PC untouched.
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 Btos ransomware, no free decryptor is known (checked 7 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 Btos 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 Btos 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 Jan 2020 · not reviewed since
Btos ransomware - yet another version in the family of Djvu/STOP virus that cannot be decrypted
Btos ransomware is a cryptovirus that makes users scared and frustrated when commonly used data becomes useless after the encryption process.
This threat comes silently and victims cannot fully understand what happened until the ransom note file _readme.txt gets placed on the desktop and in other folders with affected files. The text file includes a brief message from virus developers and statements about possible solutions and further actions.
However, since these people are focused on getting money from victims there is no reason to even consider paying the developers. It may seem like the only option since decryption is a way to get your files back but crypto-extortionists from such a huge family of malware like Djvu ransomware should not be trusted.
Especially when the recent STOPDecrypter is no longer supported that was used to recover files of many victims before. Right now this tool is not useful because major changes in the coding and encryption affected recovery options.
There are some possible solutions for versions that came out before August of 2019 because offline keys were mainly used in those processes. Newer versions, including Btos ransomware virus, fall into the category of versions that cannot be decrypted. Or at least easily.
When online keys get used for encryption, each victim gets a unique ID that identifies each particular person and their files, so criminals know what is what. Offline key usage helped researchers to develop the scheme when one key helped to decrypt many different files for victims affected by the same version of ransomware.
Some of the victims of the malware versions in this huge cryptovirus family can get help from researchers that developed Djvu decrypter, but that also involves victims with offline IDs. If your particular key involves t1 at the end, you can possibly get your files back.
Btos ransomware starts the infiltration process by entering the machine and finding files for encryption. Developers haven't changed many features of this virus, so it targets documents, images, audio, video files, and archives or databases. These are the types of files that are commonly the most important ones on the machine, so people want to get them back.
It is typical for ransomware to encrypt files as the first step of such an attack and then demand money, so other changes happen in the background when people are considering to pay the ransom.
Btos ransomware, in particular, can spread secondary payloads of malware like info-stealing trojans and worms, other malware. Also, other versions tried to mask background processes with fake Windows Update pop-up windows, so people cannot notice the infection at first.
However, there are more changes that threats like this can make on the machine, so Btos ransomware removal and file recovery process are more difficult for the person. Ransomware can:
As we mentioned, malware creators try to make it barely possible to restore files after encryption and more difficult to remove Btos ransomware by affecting these functions and features. However, even though there are fewer methods for file recovery, you can still clean the machine from this threat.
You need to rely on professional tools and scan the machine fully, so all the traces can get detected and deleted. Anti-malware tools are designed to do that, so rely on a good AV engine.
Even though your biggest concern is the recovery fo those lost files, you need to clean the machine from Btos ransomware fully until you do anything regarding data restoration, especially when it comes to data backups or third-party software. you can end up with all files encrypted if you put an external device with file backups on the infected machine.
- delete Shadow Volume Copies;
- disable programs or install other apps;
- add or alter registry entries;
- turn off security functions and features;
- load malware on the machine;
- steal data directly from the machine;
- use keyloggers and other techniques to collect valuable details.
From our report of Jan 2020 · not reviewed since
First steps when affected by ransomware
Btos ransomware as any other cryptovirus starts the attack with encryption and ransom demand that gets delivered on the pop-up window or in the text file like _readme.txt which displays the following:
The first reaction may be to contact criminals and go straight to paying, but that shouldn't be the first step. However, you need to react as soon as you get a message from virus developers and see the symptoms of the threat. Then you need to get rid of the virus and repair damage as soon as possible, so Btos ransomware cannot damage your computer permanently.
You can expect to get more information about decryption options or that researchers may update the decrypter for this family, so store at least some of the encrypted files and data related to malware, so you can have that options in the future. But clean the machine fully after that.
Also, traces of the virus can trigger different processes related to malicious Btos ransomware, so you should run a system optimizer like to check for damaged files or other affected parts of system settings or functions. Then, proceed with your chosen method of file recovery. A few additional methods can be found below.
From our report of Jan 2020 · not reviewed since
Malicious files get to be hidden in various places and disguised as safe content
It is known that ransomware is one of the most dangerous threats that stealthily infiltrates machines and can do that unnoticed.
This is because of the deceptive and misleading techniques used to spread threats like this:
To keep your device safe from such threats, you need to pay close attention to torrent sites, sharing services and cracks or game cheats you download. Content like this can include malware payload. Also, email attachments can be injected with macros that drop the ransomware, so check any notification before opening the attachment file directly on your device.
- pirated software;
- malicious files;
- other malware;
- malicious websites.
From our report of Jan 2020 · not reviewed since
Go straight to Btos ransomware termination when you notice the infection
When you get the news that Btos ransomware virus got on the device and encrypted your important files, you cannot be sure that it happened not long ago.
It is possible that malware had already affected the features and functions of the machine, so you don't have many options.
The best expert tip for Btos ransomware removal would be anti-malware programs and a full system scan that such tools can perform. The malware detection application indicates potentially dangerous files and programs, so you can see what happens on the machine.
When the scanning is done, you should be able to choose what to do or the program simply offers you to remove Btos ransomware and other threats automatically. Tools like , , or can help to check for any leftovers and possibly clean the virus damage for you.
[GI=method-1]Reboot the system in Safe Mode with Networking, so you can freely eliminate the Btos ransomware virus
[GI=method-2]System Restore feature can help with the infection and eliminate the threat by recovering the machine in a previous state
Try Windows Previous Versions
When System Restore gets enabled before, Windows Previous Versions can recover data encoded by malware. It works for individual files
ShadowExplorer - a method for file recovery
When it is known that Btos ransomware hasn't affected Shadow Volume Copies, you can use ShadowExplorer to recover files
You can try the Emisoft decryption tool for your files
Some of the versions can be decrypted with Djvu decrypter
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.
Make the next attack harmless
Btos ransomware could only hurt the files that had no second copy, and the signs (ransom notes called _readme.txt in every folder) showed exactly which ones those were.
The 3-2-1 rule fixes that:
- three copies
- two media
- one disconnected
A practical version for a home PC: OneDrive or another cloud backup with version history, plus an external disk that you plug in once a week for File History and then unplug. Test a restore now and then by opening a few files from the backup on another device.
Details, schedules and what not to back up are in our 3-2-1 backup guide for Windows.
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 Btos ransomware
Is there a free Btos ransomware decryptor?
We last checked on 7 October 2026, and for Btos 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 "Btos 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.
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.
Did Btos ransomware steal my files or passwords?
We do not know yet. Nothing published so far shows data theft by Btos ransomware, but the only confirmed sign is ransom notes called _readme.txt 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.
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 Btos ransomware get on my computer?
The way Btos 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 ransom notes called _readme.txt 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 Btos 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.
Is _readme.txt from real ransomware or a bluff?
Look at your files rather than the note. If documents and photos have a new extension and will not open, the encryption is real. If files open normally, or only a few were renamed, the note may come from fake ransomware or extortion-only malware that claims more than it did.
Some wipers also leave notes like _readme.txt while destroying data with no way back. Identification services help here too: they recognise the note and tell you whether the family is known to encrypt, to bluff, or to wipe.
How do I open my .docx, .jpg and other files locked by Btos?
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 Btos 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 Btos 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 Btos 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
- Wikipedia: Encryption (read October 7, 2026)
- Lesvirus: Lesvirus (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)