Fenrir ransomware: removal and decryption techniques

New ransom Trojan called Fenrir uses an unusual file tweaking method and proliferates via booby-trapped software downloads, clearly trying to be different.

There aren’t many ransomware species out there that go their own route in terms of the attack tactics and data impact. The specimen referred to as Fenrir is one of the few that stand out from the crowd, and here’s why. First of all, its payload is masqueraded as a legit-looking edition of Adobe Reader. This is quite offbeat as crypto viruses rarely impersonate popular software – instead, they tend to propagate through trojanized files or exploit kits. One more thing that makes Fenrir unique is that it retrieves the file extension token locally rather than go with a predefined one. It blemishes encrypted files with a suffix matching the first 10 characters of Hardware ID (HWID), an 18-character string that identifies a specific machine. And thirdly, this ransomware drops ransom notes in RTF format, while most counterparts generate .HTA, .HTML or .TXT recovery walkthroughs.

A thoroughgoing search for data ensues the Fenrir trespass event. The infection silently scans the local hard drive, inserted media if any, and network drives against a particular range of data formats. Obviously, this way the e-intruder fulfills the reconnaissance part of its objective, determining which files to encrypt based on their value to the victim. Once this list is at the ransomware’s disposal, it locks down all the spotted entries using a cryptographic standard, most likely symmetric AES with 256-bit keys. Aside from crypto, a byproduct of the data skewing workflow is the concatenation of a 10-character extension to every single ransomed item. So a file named Seaview.jpg will morph into something like Seaview.jpg.A510AG6080 as a result of these manipulations. It goes without saying that these entries become inaccessible.

To let the victim know what happened and how to sort things out, the Fenrir virus replaces the desktop wallpaper with a toxic-red screen reading, “All your files have been locked,” and leaves a manual named Ransom.rtf on the desktop. Additionally, it goes with a GUI that pops up automatically once the cipher implementation has been completed. The title of this console includes the victim’s personal ID, and the body of the window contains the same text as the ransom note mentioned above. In a nutshell, it demands $150 worth of Bitcoin for the decryption key. Having submitted the ransom, the user is supposed to send the BTC transaction ID and their victim ID to the attacker’s email address, whiterabbit01@mailinator.com. There is a deadline of 72 hours to make the payment, the remaining amount of time being reflected on the interface as well. Interestingly, the window includes a button that says, “I will not pay, delete my files!!!” However, it reportedly does nothing if clicked.

Those infected with the Fenrir virus should bear in mind that ransomware payouts encourage the threat actors to move on with their activity. So the number one tip is not to pay from the get-go. Instead, go ahead and leverage the alternative methods below to remove the infection proper and try to restore locked files.

Fenrir ransomware automated removal and data recovery

When faced with ransomware like Fenrir, one of the best shortcuts in terms of removal is to use Combo Cleaner, a lightweight and incredibly effective application with PC security and optimization features under the hood. It detects and thoroughly deletes threats while giving you insights into the overall health of your computer.

This program’s protection power spans modules that forestall all known types of malware, including ransomware and browser hijackers, and take your online security to the next level by blocking phishing sites and other suspicious web pages. Follow these simple steps to eliminate the infection for good:

1. Download Combo Cleaner installer.

Download Fenrir remover

^{Combo Cleaner scans your PC with no strings attached, but you’ll have to buy its fully functional version to remove the threats it detects. The disk optimization tools that find large files and duplicates are free to use.}

2. Open the CCSetup.exe file to get started. Several subsequent screens will allow you to make initial customizations so that the program works exactly as you need from the get-go.

3. The installation will be followed by an update of malware signatures. Once this process is through, click the Start Scan button in the left-hand sidebar.

4. Combo Cleaner will then check system locations that are most often polluted by Windows malware. The first scan can take a while to finish.

5. Combo Cleaner will display a system tray notification as soon as the scan is over. Click the Resolve found threats button to view the results.

6. The scan summary shows the names and types of the detected threats as well as their statuses and locations. Click the Remove all threats button and follow further on-screen prompts to get rid of these 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.

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

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.

Fenrir 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 Fenrir 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.

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 files ransomed by Fenrir

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.

Ransomware Prevention Tips

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

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 Fenrir removal tool