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

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. Award-winning antivirus solution for your PC. Robust security software that provides robust 24/7 real-time protection, Web Shield that stops online threats/malicious downloads, and Prevention engine that wards off Zero-Day threats. Keep your PC safe and protected against ransomware, Trojans, viruses, spyware and other forms of dangerous programs. 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: 

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. OUR GEEKS RECOMMEND 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: GeeksAdvice.com editors select recommended products based on their effectiveness. We may earn a commission from affiliate links, at no additional cost to you. Learn more. Get INTEGO ANTIVIRUS for Windows to remove ransomware, Trojans, adware and other spyware and malware variants and protect your PC and network drives 24/7. This VB100-certified security software uses state-of-art technology to provide protection against ransomware, Zero-Day attacks and advanced threats, Intego Web Shield blocks dangerous websites, phishing attacks, malicious downloads and installation of potentially unwanted programs. Use INTEGO Antivirus to remove detected threats from your computer. Read full review here. RESTORO provides a free scan that helps to identify hardware, security and stability issues and presents a comprehensive report which can help you to locate and fix detected issues manually. It is a great PC repair software to use after you remove malware with professional antivirus. The full version of software will fix detected issues and repair virus damage caused to your Windows OS files automatically. RESTORO uses AVIRA scanning engine to detect existing spyware and malware. If any are found, the software will eliminate them. Read full review here.

Method 1. Enter 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 Instructions for Windows 8/8.1/10/11 users 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.

Method 2. Use System Restore

In order to use System Restore, you must have a system restore point, created either manually or automatically. Instructions for Windows XP/Vista/7 users Instructions for Windows 8/8.1/10/11 users 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 Removing spyware and malware is one step towards cybersecurity. To protect yourself against ever-evolving threats, we strongly recommend purchasing a Premium version of Malwarebytes Anti-Malware, which provides security based on artificial intelligence and machine learning. Includes ransomware protection. See pricing options and protect yourself now.

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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.

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 BPTO, ISWR, ISZA, BPSM, ZOUU, MBTF, ZNSM (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.

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.

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.