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Decrypt .GDCB files – remove GandCrab ransomware virus

6 min read
Find out how the new GandCrab ransomware is different than the mainstream crypto threats and what methods might help restore encrypted .GDCB files.

Not only does the GandCrab ransomware stand out from the rest due to its bizarre name, but it also turns out to represent a new generation of blackmail viruses. It is competently coded and leverages a number of unconventional mechanisms that cannot be encountered elsewhere on the online extortion arena. First off, it is the only perpetrating program from this cluster that accepts ransoms in Dash cryptocurrency rather than Bitcoin, Monero or Ether. This choice of the threat actors has got some firm ground behind it – Dash is generally considered to offer a higher degree of privacy than competing platforms do. Another noteworthy trait of GandCrab is its use of the exploit kit called RIG, and more recently GrandSoft EK, to make the rounds.

Attributes of the GandCrab ransomware attack
Attributes of the GandCrab ransomware attack

The involvement of exploit kits in the propagation routine isn’t something you often see in this segment of the cybercrime ecosystem these days. Most attackers opt for more straightforward methods, such as spam or compromised RDP connections. The felons running the GandCrab campaign are, obviously, professional enough to deliver their payload via such a complex and evasive scheme. All it takes for a user to get infected is go to a hacked website that furtively redirects them to the EK. The rest is a matter of RIG or GrandSoft exploiting vulnerabilities in the host’s software behind the scenes.

When up and running on a computer, the GandCrab ransomware ends a few dozen processes that might prevent it from completing the crypto job. Specifically, if any valuable file is in use by one of these processes, the subsequent workflow of encrypting this particular file may fail. Next, the baddie attempts to establish connection with its Command and Control server, which is a .bit domain. If this part of the attack chain is successful and the culprit receives the public RSA key from the C2, it starts encrypting the victim’s files matching a hard-coded list of popular data formats. When done, GandCrab subjoins the .GDCB extension to every single object that was encrypted (Sample.jpg becomes Sample.jpg.GDCB). Copies of the ransom note named GDCB-DECRYPT.txt, which the Trojan sprinkles all over the system, instruct the user to visit a specified Tor page named GandCrab Decryptor. This page includes the following information: the victim’s operating system and country based on their IP address; the size of the ransom (1.54 Dash, or about $1200) along with the Dash address for payment; and a script displaying the countdown of four days. If the plagued user does not fit in this deadline, the ransom will double.

In summary, the GandCrab ransomware is shaping up to be a new major player on the extortion landscape. It is skillfully crafted, innovative, and its distribution is gearing up for a rise. The starting point in this attack scenario is to use the tried-and-true data recovery tricks below based on the best forensic practices. Coughing up the ransom is a dangerous game as it may turn out futile and the hostage files will remain inaccessible regardless.

GandCrab ransomware automated removal and data recovery

When dealing with the GandCrab threat, you can get a lot of mileage out of the Malwarebytes automatic security tool that will pinpoint and iron out the infection in minutes. Malwarebytes is one of the big names in the anti-malware industry with an immaculate track record of protecting systems against all prevalent forms of harmful code.

The solution uses artificial intelligence (AI) and machine learning to detect both known and zero-day threats, including potentially unwanted programs (PUPs), ransomware, exploits, and malicious sites. It boasts low system footprint, high scanning speed, and intuitive interface where every module clearly explains what it does. Follow the steps below to come through the malware predicament unscathed:

1. Download and install the latest version of Malwarebytes onto your PC.

As part of this step, you will be prompted to specify where you are installing the program (personal or work computer) and toggle the advanced setup options if you so desire. You can use all the premium features for 14 days free of charge.

Download GandCrab virus remover

2. Once the application is up and running, go ahead and click on the Scan button in the bottom middle part of the GUI.Click the Scan button

3. Wait until Malwarebytes checks for updates of its proprietary Katana detection engine and scans the memory, startup items, registry, and file system for threats.Malwarebytes scan in progress

4. When the scan is completed, go over the report listing the infections that have been identified. Make sure there are checkmarks next to all the unwanted items and click on the Quarantine button as shown below.Malwarebytes scan results

5. You will be prompted to restart your computer to finish the removal process. Click Yes to do it immediately or close the dialog and restart later on.Restart to complete the removal process

6. As soon as the threats have been moved to Quarantine, they can no longer harm your computer. If you are sure that you won’t need to restore any of those items at a later point, click on the Detection History pane at the bottom left of the Malwarebytes home screen, select the Quarantined items tab, and click Delete.Delete quarantined items

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 Stellar Data Recovery features this type of a capability and therefore it can be applied in ransom attack scenarios to at least get the most important files back. So use the app to get an idea of what data can be restored and let it do the recovery job. Here is a step-by-step walkthrough:

1. Download and install Stellar Data Recovery.

Download Stellar Data Recovery

2. Open the application, select the types of recoverable files to look for, and click Next.Stellar Data Recovery main screen

3. Choose the areas you want the tool to recover from and click the Scan button.Select which PC areas to recover from

4. Having scanned the specified locations, the program will display a notification about the total amount of recoverable data. Close the dialog and click the Recover button. This will hopefully help you get some of your valuable files back.Recover files

GandCrab 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 GandCrab 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 GandCrab ransomware using Safe Mode with Networking

Remove GandCrab ransomware using Safe Mode with Networking

Get rid of GandCrab ransomware using System Restore

Get rid of GandCrab 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 .GDCB 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 GandCrab ransomware, 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.

Ransomware Prevention Tips

To avoid GandCrab 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. Another benefit of using the antimalware tool is that it will keep ransomware threats from intruding on your computer further on.

Download GandCrab ransomware removal tool

One Comment

  1. Eric Afanador

    February 13, 2018 at 2:51 am

    Recovery and data


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