Remove BTOS Ransomware Virus (2022 Guide)

BTOS ransomware targets inattentive Windows users to encrypt their files

BTOS ransomware is a malicious virus designed to encrypt personal files on Windows operating systems. It is the 202nd version of STOP/DJVU virus. The ransomware encrypts files using RSA and marks them with .btos file extensions. The virus then creates a ransom note in _readme.txt file, which commands contacting cybercriminals via helpmanager@firemail.cc or helpmanager@iran.ir emails. 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. To decrypt .btos 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 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, so please jump to instructions provided below the article to accomplish this task.

Threat Summary

Name	BTOS ransomware virus
Type	File-encrypting virus
Origins	STOP/DJVU (202th version)
Targeted systems	Windows
Behavior	Encrypts files, restricts access to them and demands paying a ransom (according to instructions in _Readme.txt file)
Extension	Appends .btos file extension to files
Ransom note	_readme.txt
Ransom demand	$490-$980
Emails	helpmanager@firemail.cc or helpmanager@iran.ir
Distribution	Hides in illegal online downloads, such as KMSPico
Decryption tools	STOP Decryptor doesn’t support this extension at the moment
Removal	Remove using antivirus while in Safe Mode (see instructions below)

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 helpmanager@firemail.cc or helpmanager@iran.ir. 

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: 

1. Go to C:/SystemID/PersonalID.txt.
2. 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

Computer users willing to avoid BTOS ransomware attack should stay away from illegal online downloads, including:

• Software cracks;
• Software license keygens;
• Illegal peer-to-peer downloads;
• Suspicious adware;
• Other shady files.

The STOP ransomware family variants such as TOPI, NOSU, REHA, 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. 

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 removing malware using a professional antivirus software and then using the following tool to repair virus damage to Windows system files:

REPAIR VIRUS DAMAGE TO YOUR COMPUTER

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