Remove BTOS Ransomware Virus (DECRYPT .btos FILES)
BTOS ransomware reemerges in 2022 to attack computer users again
Contents
BTOS ransomware is file-encrypting virus designed to infect Windows-running computers. This ransomware encrypts files using military-grade encryption and marks them with .btos file extensions. First emerged in 2020, it appeared to be the 202nd version of STOP/DJVU virus, although in December 2022, cybercriminals released 618th variant using the same extension. After encrypting all data, the virus creates a ransom note named as _readme.txt, which commands the victim to contact cybercriminals via provided email addresses. The virus seeks to extort the victim and receive a ransom worth $490 or $980 in Bitcoin.
BTOS virus uses a strong file encryption algorithm to make data inaccessible to the victim. The point of encryption is to secure data so that only the particular individual could see it. The malware also renames the files as explained in the following example: 1.jpg becomes 1.jpg.btos, 2.docx becomes 2.docx.btos and so on.
To decrypt such encrypted file, a private decryption key is required, which is held by the cybercriminals. Unfortunately, it is inaccessible to the victims or cybersecurity researchers. Trying to crack it would take years, so it is out of the question.
The described STOP/DJVU variant enters the system alongside illegal online downloads and starts encrypting personal files right away. It must be noted that the ransomware encrypts the first 150KB of files, adding 334 bytes to the original file size due to usage of RSA-encrypted key, victim’s ID and filemarker. During the data corruption procedure, the virus leaves _readme.txt notes in each folder containing the files. Finally, the malware deletes system restore points which are often the victim’s last resort when it comes to data recovery.
What is even worse, BTOS virus tends to install password-stealing Trojans such as Azorult or VIDAR on the system. Therefore, if you have been attacked by this DJVU variant, consider all of your passwords stolen. You must eliminate the malware from your system and change your passwords then.
The best way to remove BTOS ransomware virus is in Safe Mode with Networking, so please jump to instructions provided below the article to accomplish this task. We recommend using INTEGO Antivirus for assistance with malware removal. Speaking of repairing damaged Windows OS files, download RESTORO for the task.
Ransomware Summary
| Name | BTOS Ransomware Virus |
| Type | Ransomware; Crypto-malware; Virtual Extortion Virus |
| Family | STOP/DJVU |
| Encryption type | RSA 2048 + Salsa20 |
| Previous versions | MATU, MAOS, BTNW, BTOS, BTTU, MBTF, MPPN (find full list here) |
| Version | 202nd and 618th |
| Extension | .btos |
| Cybercriminal emails | helpmanager@firemail.cc and helpmanager@iran.ir (2020 variant) or support@fishmail.top and datarestorehelp@airmail.cc (2022 variant) |
| Additional malware dropped | Azorult or Vidar Trojan |
| Damage | The ransomware uses encryption to maliciously modify all files on the PC and marks their original names with .btos extension. Ransom notes called as _readme.txt will be dropped in every computer folder. This piece of malware usually drags VIDAR Stealer alongside it and also eliminates VSS from the system. On top of that, it tends to modify Windows HOSTS file to restrict computer user’s access to cybersecurity-related websites online. |
| Ransom note | _readme.txt |
| Ransom demand | $490-$980 in Bitcoin |
| Distribution | Victims often download this ransomware along illegal torrent downloads, cracked software, activators, key generators or tools like KMSPico. |
| Known software cracks to contain this malware | Corel Draw, Tenorshare 4ukey, Adobe Photoshop, Cubase, Adobe Illustrator, Internet Download Manager, Tally, League of Legends. |
| Detection names | Trojan:Win32/Azorult.FW!MTB (Microsoft), Gen:Heur.Mint.Zard.52 (B) (Emsisoft), HEUR:Trojan.Win32.Scarsi.gen (Kaspersky), Gen:Heur.Mint.Zard.52 (BitDefender), Trojan.MalPack.GS (Malwarebytes), ML.Attribute.HighConfidence (Symantec) see all detection name variations on VirusTotal |
| Removal | Remove ransomware and related malware from your PC using trustworthy software like INTEGO Antivirus. To repair virus damage on Windows OS files, download and try RESTORO (secure download link). |
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Ransom demands stated in the note
BTOS file virus creates _readme.txt note to inform the victim about the cyberattack and state the further steps the victim must take if he/she wants to restore the data one day. According to the ransom note, all documents, databases and other files have been encrypted, and the only method to recover them is to pay the ransom.
The attackers suggest proving their abilities to recover data – the victim can send one small file for decryption. The further instructions on payment can be received by contacting the attackers via provided emails: helpmanager@firemail.cc or helpmanager@iran.ir (2020 version of this file extension malware) or support@fishmail.top and datarestorehelp@airmail.cc (2022 variant).
Data recovery is possible if encrypted with an offline key
During the data encryption, the described virus first attempts to establish a connection with its Command & Control server. Such a step is required to obtain individual ONLINE encryption keys for each victim. However, if the connection fails, the virus then uses a hardcoded OFFLINE encryption key to corrupt data.
The offline key is identical for all versions of BTOS extension virus. Once someone encrypted with offline key pays a ransom, the key then can be used by all victims of offline encryption. Therefore, we suggest you to keep checking for updates in this STOP/DJVU decryption guide.
You can check whether you’re subject to the offline encryption this way:
- Go to C:/SystemID/PersonalID.txt.
- Here, check the ending symbols of the ID or IDs stored here. If any of them ends in t1, it is an indicator of an offline encryption. All other cases mean online encryption.
DJVU distribution relies on illegal downloads
In general, STOP/DJVU variants are mainly distributed through illegal online downloads that cybercriminals present as software cracks, movies and other copyright-protected content. Computer users willing to avoid BTOS ransomware attack should stay away from the following:
- Software cracks;
- Software license keygens;
- Illegal peer-to-peer downloads;
- Suspicious adware;
- Other shady files.
The STOP ransomware family variants such as MAOS, MPPN, MATU, or others are well-known to be included in malicious downloads such as KMSPico, so make sure you resist the temptation to install paid software for free. The risk of losing all of your data is very high.
Another commonly used ransomware distribution method is malicious email spam containing attachments. The criminals seek to convince the target to launch email attachments that contain some harmful code. This code is then used to download the malware from an external source and run it on the system.
Therefore, computer users should stay vigilant and inspect every email for red flags that tell the sender’s intentions are malevolent, such as: urgent message tone, grammar mistakes, generic greeting line, such as Dear customer/Valued client, spoofed sender’s email address, low-quality logos and images.
Remove BTOS ransomware virus effectively
You must remove BTOS ransomware virus along with password-stealing Trojans it has installed on your computer. Successful elimination of the ransomware and its remains is essential when reacting to this type of cyberattack.
Following a BTOS virus removal, you should replace all of your passwords. Since the password-stealing Trojans tend to steal them from browser’s memory, try changing these passwords first. When it comes to .btos data recovery, check for your data backups, as this is the only way of restoring data corrupted by this virus variant now.
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Our team recommends a two-step rescue plan to remove ransomware and other remaining malware from your computer, plus repair caused virus damage to the system:
STEP 1. REMOVE AUTOMATICALLY WITH ROBUST ANTIVIRUS
STEP 2. REPAIR VIRUS DAMAGE TO YOUR COMPUTER
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BTOS Ransomware Virus Removal Guidelines
Method 1. Enter Safe Mode with Networking
Step 1. Start Windows in Safe Mode with Networking
Before you try to remove BTOS Ransomware Virus virus, you must start your computer in Safe Mode with Networking. Below, we provide the easiest ways to boot PC in the said mode, but you can find additional ones in this in-depth tutorial on our website – How to Start Windows in Safe Mode. Also, if you prefer a video version of the tutorial, check our guide How to Start Windows in Safe Mode on Youtube.
Instructions for Windows XP/Vista/7 users
- First of all, turn off your PC. Then press the Power button to start it again and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. This launches the Advanced Boot Options menu.
- Use arrow keys on the keyboard to navigate down to Safe Mode with Networking option and press Enter.
Instructions for Windows 8/8.1/10/11 users
- Open Windows Start menu, then press down the Power button. On your keyboard, press down and hold the Shift key, and then select Restart option.
- This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
- In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Networking. In this case, it is the F5 key.
Step 2. Remove files associated with the virus
Now, you can search for and remove BTOS Ransomware Virus files. It is very hard to identify files and registry keys that belong to the ransomware virus, Besides, malware creators tend to rename and change them repeatedly. Therefore, the easiest way to uninstall such type of a computer virus is to use a reliable security program such as INTEGO Antivirus. For virus damage repair, consider using RESTORO.
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Method 2. Use System Restore
In order to use System Restore, you must have a system restore point, created either manually or automatically.
Step 1. Boot Windows in Safe Mode with Command Prompt
Instructions for Windows XP/Vista/7 users
- Shut down your PC. Start it again by pressing the Power button and instantly start pressing F8 button on your keyboard repeatedly in 1-second intervals. You will see Advanced Boot Options menu.
- Using arrow keys on the keyboard, navigate down to Safe Mode with Command Prompt option and press Enter.
Instructions for Windows 8/8.1/10/11 users
- Launch Windows Start menu, then click the Power button. On your keyboard, press down and hold the Shift key, and then choose Restart option with the mouse cursor.
- This will take you to Windows Troubleshoot screen. Choose Troubleshoot > Advanced Options > Startup Settings > Restart. Tip: If you can't find Startup Settings, click See more recovery options.
- In Startup Settings, press the right key between F1-F9 to enter Safe Mode with Command Prompt. In this case, press F6 key.
Step 2. Start System Restore process
- Wait until system loads and command prompt shows up.
- Type cd restore and press Enter, then type rstrui.exe and press Enter. Or you can just type %systemroot%system32restorerstrui.exe in command prompt and hit Enter.
- This launches System Restore window. Click Next and then choose a System Restore point created in the past. Choose one that was created before ransomware infection.
- Click Yes to begin the system restoration process.
After restoring the system, we recommend scanning the system with antivirus or anti-malware software. In most cases, there won't be any malware remains, but it never hurts to double-check. In addition, we highly recommend checking ransomware prevention guidelines provided by our experts in order to protect your PC against similar viruses in the future.
Alternative software recommendations
Malwarebytes Anti-Malware
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Decrypt BTOS files
Fix and open large BTOS files easily:
It is reported that STOP/DJVU ransomware versions encrypt only the beginning 150 KB of each file to ensure that the virus manages to affect all files on the system. In some cases, the malicious program might skip some files at all. That said, we recommend testing this method on several big (>1GB) files first.
- Create a copy of encrypted file to a separate folder using Copy > Paste commands.
- Now, right-click the created copy and choose Rename. Select the BTOS extension and delete it. Press Enter to save changes.
- In the prompt asking whether you want to make the changes as file might become unusable, click OK.
- Try opening the file.
STOP/DJVU decryption tool usage guide
STOP/DJVU ransomware versions are grouped into old and new variants. BTOS Ransomware Virus is considered the new STOP/DJVU variant, just like MATU, MAOS, BTNW, BTOS, BTTU, MBTF, MPPN (find full list here). This means full data decryption is now possible only if you have been affected by offline encryption key. To decrypt your files, you will have to download Emsisoft Decryptor for STOP DJVU, a tool created and maintained by a genius security researcher Michael Gillespie.
Note! Please do not spam the security researcher with questions whether he can recover your files encrypted with online key - it is not possible.
In order to test the tool and see if it can decrypt BTOS files, follow the given tutorial.
- Download the decryption tool from Emsisoft.
- Click the little arrow next to your download and choose Show in Folder.
- Now, right-click the file and choose Run as Administrator. If asked, enter administrator's password.
- In UAC window, click Yes.
- Click Yes to agree to software terms in both windows.
- The tool will automatically include C:// disk as a location to decrypt. The file recovery tool will prepopulate the locations to scan, including connected data storage drives or network drives. Click Add folder if you wish to add additional locations.
In Options tab, you can choose to keep encrypted file copies. We recommend leaving this option selected, especially if you do not know if the decryption tool will work. - Click Decrypt to start restoring BTOS files. You will see the progress in the Results tab. Here, you can see messages from the tool, such as whether the decryption procedure is successful, or you need to wait for an update.
You might also be informed that online key was used to encrypt your files. In such case, the decryption tool won't work for you, and the only way to recover your files is to use a data backup.
Meanings of decryptor's messages
The BTOS decryption tool might display several different messages after failed attempt to restore your files. You might receive one of the following messages:
Error: Unable to decrypt file with ID: [example ID]
This message typically means that there is no corresponding decryption key in the decryptor's database.
No key for New Variant online ID: [example ID]
Notice: this ID appears to be an online ID, decryption is impossible
This message informs that your files were encrypted with online key, meaning no one else has the same encryption/decryption key pair, therefore data recovery without paying the criminals is impossible.
Result: No key for new variant offline ID: [example ID]
This ID appears to be an offline ID. Decryption may be possible in the future.
If you were informed that an offline key was used, but files could not be restored, it means that the offline decryption key isn't available yet. However, receiving this message is extremely good news, meaning that it might be possible to restore your BTOS extension files in the future. It can take a few months until the decryption key gets found and uploaded to the decryptor. We recommend you to follow updates regarding the decryptable DJVU versions here. We strongly recommend backing up your encrypted data and waiting.
Report Internet crime to legal departments
Victims of BTOS Ransomware Virus should report the Internet crime incident to the official government fraud and scam website according to their country:
- In the United States, go to the On Guard Online website.
- In Australia, go to the SCAMwatch website.
- In Germany, go to the Bundesamt für Sicherheit in der Informationstechnik website.
- In Ireland, go to the An Garda Síochána website.
- In New Zealand, go to the Consumer Affairs Scams website.
- In the United Kingdom, go to the Action Fraud website.
- In Canada, go to the Canadian Anti-Fraud Centre.
- In India, go to Indian National Cybercrime Reporting Portal.
- In France, go to the Agence nationale de la sécurité des systèmes d’information.
If you can't find an authority corresponding to your location on this list, we recommend using any search engine to look up "[your country name] report cyber crime". This should lead you to the right authority website. We also recommend staying away from third-party crime report services that are often paid. It costs nothing to report Internet crime to official authorities.
Another recommendation is to contact your country's or region’s federal police or communications authority.
Frequently Asked Questions
You can only open BTOS files if you have the decryption key, or if you were affected by offline encryption type.
To figure out whether you were affected by offline encryption, please go to C:/SystemID/PersonalID.txt and see if the string inside of it ends in t1. You can also try using Emsisoft Decryptor for STOP/DJVU.
Please follow the guidances provided by the official BTOS decryption tools and believe what they say. If they say it is impossible to decrypt, it really is so. There is no magic tool or human capable of decrypting your files hiding somewhere. Encryption is a technique created to be nearly impossible to decrypt without a special private key (held by the criminals).
We advise scanning with anti-virus, anti-malware, malware removal tools or software like RESTORO to eliminate virus damage on the system. If you do not trust using a single tool, try running one after another. However, we do not recommend keeping several security programs on a computer at once as they can interfere with each other's work.
Beware of fake BTOS decryption tools circulating around the web. Cyber criminals are uploading them to various shady websites, also might be promoting them via suspicious Youtube videos. These programs can infect your computer even more heavily (Trojans, miners, etc.). We suggest being extremely cautious around the web. If there will be an official STOP/DJVU decryption tool available, it will be widely discussed in public media.
Norbert Webb is the head of Geek’s Advice team. He is the chief editor of the website who controls the quality of content published. The man also loves reading cybersecurity news, testing new software and sharing his insights on them. Norbert says that following his passion for information technology was one of the best decisions he has ever made. “I don’t feel like working while I’m doing something I love.” However, the geek has other interests, such as snowboarding and traveling.
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