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Decrypt .master ransomware files – BTCWare virus variant

6 min read
A new version of the BTCWare ransom Trojan is out that appends the .master extension to encrypted files and drops a ransom note named !#_RESTORE_FILES_#!.inf.

The evolution of the BTCWare crypto hoax is underway. Its latest edition has introduced a few external tweaks, while on the inside it is still the same, quite professionally tailored ransomware. The IOCs (indicators of compromise) accompanying this recent update include the .master extension being affixed to every scrambled file, as well as a new ransom note named !#_RESTORE_FILES_#!.inf. The above-mentioned file extension token proper is preceded by an email address in square brackets, so a sample file Pic.jpg will look like this: Pic.jpg.[BM-RBM3FiE47xgnUUpzrRPwlMlSEaV3qxwa@protonmail.ch].master, or similar. The attackers’ email address may vary. For instance, it may be look1213@protonmail.com, kry.right@india.com, unlocking.guarantee@aol.com, makedonskiy@gmx.com, predatorthre@bigmir.net, or help@onyon.info. By the way, some scarce reports are coming in about a likely successor of this BTCWare variant, which concatenates the .[3bitcoins@protonmail.com].blocking extension to hostage files.

!#_RESTORE_FILES_#!.inf ransom note
!#_RESTORE_FILES_#!.inf ransom note

The wording of the !#_RESTORE_FILES_#!.inf ransom how-to has changed as well and is now more detailed. Now it starts with the following alert, “What happened? Your important files produced on this computer have been encrypted due a security problem. If you want to restore them, write to us to the e-mail: [attacker’s_email_addresses]. You have to pay for decryption in Bitcoins. The price depends on how fast you write to us. After payment we will send you the decryption tool that will decrypt all your files.” A few other paragraphs in the ransom note are related to test decryption of up to 3 files that are less than 1 MB in size; instructions on how to obtain Bitcoins; and recommendations to refrain from renaming encrypted files and trying to restore data using third party software. According to the warning, the deadline for contacting the crooks is 36 hours – after this period expires, the decryption key will purportedly be deleted from the C2 server.

Payment site used by the .master file ransomware
Payment site used by the .master file ransomware

Infected users who reach out to the felons get further recovery directions in response. In particular, they are told to visit a specific page that requests 0.5 BTC (about 1400 USD). A victim needs to send this amount to a Bitcoin address indicated on the “Recovery files” page, enter the corresponding transaction ID to get the decryption key, and then enter several CMD commands to initiate the .master files decryption process. Of course it’s up to the user whether they pay or not, but there can be no certainty that the outcome will be as expected.

Just like the previous BTCWare editions, the .master file virus hits computers mostly via compromised RDP connections. In other words, the malefactors deploy the bad code manually once they have direct access to the target host. With that said, it’s within the realms of possibility that the payload may also make the rounds by means of malicious spam attachments. It’s also noteworthy that this ransomware specimen employs MS CryptoAPI for data encryption. The specific algorithm being used is the symmetric AES-192. Security analysts have had some success decrypting earlier BTCWare spinoffs, but these free recovery tools have limited support of the most recent .master extension version so far. So it’s recommended to start troubleshooting with the workarounds covered in the next few sections of this post.

.Master ransomware automated removal and data recovery

Owing to an up-to-date database of malware signatures and intelligent behavioral detection, the recommended software can quickly locate the infection, eradicate it and remediate all harmful changes. So go ahead and do the following:

1. Download and install the antimalware tool. Open the solution and have it check your PC for PUPs and other types of malicious software by clicking the Start Computer Scan button

Download .master ransomware remover

2. Rest assured the scan report will list all items that may harm your operating system. Select the detected entries and click Fix Threats to get the troubleshooting completed.

Data recovery toolkit to the rescue

Some strains of ransomware are known to delete the original files after the encryption routine has been completed. As hostile as this activity appears, it can play into your hands. There are applications designed to revive the information that was obliterated because of malfunctioning hardware or due to accidental removal. The tool called Data Recovery Pro by ParetoLogic features this type of capability therefore it can be applied in ransom attack scenarios to at least get the most important files back. So download and install the program, run a scan and let it do its job.

Download Data Recovery Pro

Data Recovery Pro

.Master ransomware manual removal and file recovery

Some ransomware strains terminate themselves after completing the encryption job on a computer, but some don’t. Furthermore, the .master file virus may prevent victims from using popular antimalware tools in order to stay on board for as long as possible. Under the circumstances, it may be necessary to utilize the Safe Mode with Networking or System Restore functionality.

Remove .master ransomware using Safe Mode with Networking

Remove .master ransomware using Safe Mode with Networking

Boot into Safe Mode with Networking. The method to do it depends on the version of the infected operating system. Follow the instructions below for your OS build.

  • Restart the machine. When the system begins loading back up, keep pressing the F8 key with short intervals. The Windows Advanced Options Menu (Advanced Boot Options) screen will appear.Boot into Safe Mode with Networking on Windows Vista and 7
  • Use arrow keys to select Safe Mode with Networking and hit Enter. Log on with the user account infected by the ransomware.
  • Click on the Search icon next to the Start menu button. Type msconfig in the search field and select the System Configuration option in the results. Go to the Boot tab in the upper part of the GUI.Boot options on Windows 8, 8.1 and 10
  • Under Boot options, select Safe boot and click the Apply button. A prompt will appear to reboot the computer so that the changes take effect. Select the Restart option and wait for the system to load into Safe Mode. Again, log on with the ransomware-stricken user account.

In Safe Mode, the ransom Trojan won’t keep security software from running or otherwise thwart troubleshooting. Open your preferred web browser, download and install an antimalware tool of choice and start a full system scan. Have all the detected ransomware components removed in a hassle-free way.

Get rid of .master ransomware using System Restore

Get rid of .master ransomware using System Restore

System Restore enables Windows users to roll back all changes made to the OS since the latest restore point creation time. This feature can help eliminate the most persistent ransomware. Before going this route, though, make sure System Restore had been enabled prior to the breach, otherwise the method will be inefficient.

  • Open Windows Advanced Options Menu as described in the previous section: hit F8 repeatedly when the PC is starting up. Use arrow keys to highlight the Safe Mode with Command Prompt entry. Hit Enter.Safe Mode with Command Prompt
  • In the Command Prompt window, type cd restore and hit Entercd restore command
  • Type rstrui.exe in the new command line and press EnterType rstrui.exe command
  • When the System Restore screen pops up, click Next, select a restore point that predates the contamination, and use the application’s controls to roll back the system to this earlier state.System Restore window

Be advised that even after the ransomware is removed, files will still be encrypted and inaccessible. The malicious code cleanup part, however, is important because it keeps a relapse of the infection from occurring further on and eliminates all opportunistic malware.

Ways of non-ransom recovery of .master extension files

Cracking the crypto used by this ransom Trojan is more of a science fiction thing rather than an attainable prospect for the masses. This is why the troubleshooting in predicaments of this sort is a matter of two approaches: one is to pay the ransom, which isn’t an option for many victims; and the other is to apply instruments that take advantage of the ransomware’s possible weaknesses. If the latter is your pick, the advice below is a must-try.

Backups can make your day

Backups can make your day

Not only are you a lucky person in case you’ve been backing up your most important files, but you’re also a wise and prudent user. This isn’t necessarily a resource-heavy activity these days – in fact, some providers of online services are allocating a sufficient size of cloud storage space for free so that every customer can easily upload their critical data without paying a penny. Having removed the .master file variant of BTCWare, therefore, all you have to do is download your stuff from the remote server or transfer it all from an external piece of hardware if that’s the case.

Restore previous versions of encrypted files

Restore previous versions of encrypted files

A positive upshot of using this technique depends on whether or not the ransomware has erased the Volume Shadow Copies of the files on your PC. This is a Windows feature that automatically makes and keeps the backups of data elements on the hard drive as long as System Restore is enabled. The cryptoware in question is programmed to switch off the Volume Shadow Copy Service (VSS), but it has reportedly failed to in some cases.

Checking one’s options regarding this workaround is doable in two ways: through the Properties menu of each file or by means of the remarkable open-source tool called Shadow Explorer. We recommend the software-based way because it’s automated, hence faster and easier. Just install the app and use its intuitive controls to get previous versions of the encrypted objects reinstated.
Shadow Explorer

Alternatively, you can leverage the Previous Versions feature, which is native to Windows operating system. This method is more cumbersome that the use of ShadowExplorer, but it can help restore the most important individual files on condition that the ransomware failed to disable the Volume Snapshot Service on the computer. Right-click on a file of choice and select Properties. Then, go to the Previous Versions tab as illustrated below.
Previous Versions

Go ahead and pick the file’s latest backup version on the list. Use the Copy or Restore buttons to reinstate this object to a new path or to its original folder, respectively.

Use BTCWareDecrypter tool to restore .master files

Michael Gillespie, well-known malware researcher and author of the ID Ransomware service, released a free decryption utility that cracks most variants of BTCWare. Although this tool, BTCWareDecrypter, may have limited support of newer spinoffs of this ransomware lineage, it is definitely worthwhile as a recovery option.

1. Download BTCWareDecrypter. Open the ZIP file and double-click on BTCWareDecrypter.exe file to run the app
BTCWareDecrypter GUI

2. To proceed, you need an arbitrary encrypted file and its unencrypted (original) copy. Go to Settings and select the Find Key option. Use Browse buttons to select and upload the two files
BruteForcer module of BTCWareDecrypter

3. Click on Start to launch the app’s BruteForcer component. It will notify with a dialog box you when it finds the decryption key. If this routine is successful and the key is retrieved, select a directory to be decrypted, and click on Decrypt button. Wait until BTCWareDecrypter restores your hostage files. Be advised this process may take quite some time.

Ransomware Prevention Tips

To avoid .master ransomware and other file-encrypting infections in the future, follow several simple recommendations:

  • Toggle your email provider’s anti-spam settings to filter out all the potentially harmful incoming messages. Raising the bar beyond the default protection is an important countermeasure for ransom Trojans

  • Define specific file extension restrictions in your email system. Make sure that attachments with the following extensions are blacklisted: .js, .vbs, .docm, .hta, .exe, .cmd, .scr, and .bat. Also, treat ZIP archives in received messages with extreme caution

  • Rename the vssadmin.exe process so that ransomware is unable to obliterate all Shadow Volume Copies of your files in one shot

  • Keep your Firewall active at all times. It can prevent crypto ransomware from communicating with its C&C server. This way, the threat won’t be able to obtain cryptographic keys and lock your files

  • Back up your files regularly, at least the most important ones. This recommendation is self-explanatory. A ransomware attack isn’t an issue as long as you keep unaffected copies of your data in a safe place

  • Use an effective antimalware suite. There are security tools that identify ransomware-specific behavior and block the infection before it can do any harm.
These techniques are certainly not a cure-all, but they will add an extra layer of ransomware protection to your security setup.

Revise your security status

Post-factum assessment of the accuracy component in malware removal scenarios is a great habit that prevents the comeback of harmful code or replication of its unattended fractions. Make sure you are good to go by running an additional safety checkup.

Download .master ransomware removal tool

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