Home Guides Arena virus: how to recover .arena extension files (Dec. 2017)

Arena virus: how to recover .arena extension files (Dec. 2017)

6 min read
New persona of the Crysis ransomware has been released that appends the .arena extension to encrypted data and still implements encryption securely.

The crypto ransomware breed known as Crysis, or Dharma, appears to be gearing up for a rise. It has been spawning malicious descendants almost on a weekly basis since early August 2017, having been in an idle state for months on end. The latest offshoot has introduced the .arena file extension token to the digital extortion environment. After encrypting a victim’s personal data, this Crysis mod appends original filenames with a variant-specific string in the following format: id-{victim ID}.[chivas@aolonline.top].arena. The variable part is a unique identifier assigned to the infected user. It consists of eight hexadecimal characters. Ultimately, the ransomware turns a file named Sample.docx into something like Sample.docx.id-CFABE140.[chivas@aolonline.top].arena.

Encrypted files with the .arena extension
Encrypted files with the .arena extension

The email address provided in square brackets may vary too as it matches a specific attacker’s contact details. The thing is, the Crysis/Dharma ransomware is being distributed by several cybercriminal rings that run independent campaigns, hence different contact information of each group. Some of the most widely reported emails, aside from the one mentioned above, include:

  • m.heisenberg@aol.com
  • macgregor@aolonline.top
  • black.mirror@qq.com
  • btc2017@india.com
  • gladius_rectus@aol.com
  • sindragosa@bigmir.net
  • sir.dragcsa@bigmir.net
  • mandanos@foxmail.com

Anyone confronted with this file-encrypting malware strain therefore gets some clues on what to do next, at least in terms of contacting the threat actors via email.

Info.hta rescue note by Arena ransomware
Info.hta rescue note by Arena ransomware

Victim interaction through filename components alone, though, is definitely scarce. So the Arena ransomware also sprinkles rescue notes across the contaminated system. These are files with detailed instructions on paying the ransom and restoring the skewed data. The Crysis version in question uses the following combo for this purpose: Info.hta and FILES ENCRYPTED.txt. The latter says, literally, “All your data has been locked us. You want to return? Write email chivas@aolonline.top,” or whatever the address is. The latter file, the HTA one, gets displayed automatically due to an autorun task and includes much more information than the TXT counterpart. It reads, “All your files have been encrypted due to a security problem with your PC. If you want to restore them, write us to the email.” At the end of the day, the victim is instructed to shoot a message to the crooks, indicating their personal ID in the email title. The felons will then get back to the user with the size of the ransom and the Bitcoin wallet address to submit it.

The .arena file variant of the Crysis ransomware most commonly propagates via hacked remote desktop services. A lot of people use default or ridiculously easy-to-guess RDP credentials, and online perpetrators definitely know it. Having landed onto a system, the infection attempts to delete shadow copies of the victim’s files in order to prevent this vector of recovery. To top it off, the pest leverages best practices of data encryption, so there is no way to decrypt files for free at this point. However, in case the Arena virus fails to disable VSS, chances are some files can be restored to their normal state. See below for additional details.

Arena ransomware automated removal and data recovery

When faced with ransomware like Arena, 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 Arena 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.

Download and run Combo Cleaner installer on your PC

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.Setup customizations

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.Start initial scan

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.Combo Cleaner scan in progress

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.Scan completed

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.Scan results

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

Arena 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 Arena 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 Arena ransomware using Safe Mode with Networking

Remove Arena ransomware using Safe Mode with Networking

Get rid of Arena ransomware using System Restore

Get rid of Arena 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 .arena 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 Arena 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 Arena 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 Arena removal tool


  1. Mark Gardner

    September 5, 2017 at 12:16 pm

    I did purchase Recovery Pro in an attempt to recover some of the files the “Arena” ransomware encrypted but, as described in much of the recent documentation, the command line in the package is very successful at removing shadow copies.
    All I can say is “BACKUP BACKUP BACKUP”


  2. Tiji Thomas

    October 4, 2017 at 9:30 am

    Dear Team,
    Lastweek my server attacked ransomware virus arena, my software files all are encrypted, all the jpeg, pdf files are encrypted.
    unfortunately i don’t have backup for the software. the server is Virtual machine (HyperV). My software backup file is created inside the folder that extension is (.sbs). is there any way to retrieve the data from this file. can you please help me for this. this is very

    Tiji Thomas


  3. Kayne

    November 10, 2017 at 5:53 pm

    For people with this I lost 200TB due to leaving my RDP open because I wanted to work at home. (oops) Also requesting it is pointless as if there was a solution, it would not be a problem. Every anti-malware/ransomware programs would already have it.

    Here is a reply I got from 2 of the largest data recovery companies:

    “..As mentioned, there is no known program that can recover something encrypted, since there is no way for a program to get ahold of the unique decryption key for each different infection.” -Paratologic

    “..Note that AppCheck is for proactive defense, not a decryption tool because there’s no way to recover the encrypted files once it is encrypted by Ransomware. ” -AppCheck

    The only light at the end of the tunnel is to hang on to your encrypted software as in a few months the decryptor/key surfaces, usually on the darkweb first and then slowly though forums and sites. Until then, you’ll have to do what I am doing, and rebuilding from scratch (sadly, my personal stuff is irreplaceable)

    And while it may seem to late now, get an unlimited backup plan (there are lots that start at $5/month) and start backing up. If it happened once, it will happen again.

    Also note, that this malware is only obtainable from unscrupulous activity (i.e. your bank, or email provider is not going to do this to you), cuold have been something simple like a torrent movie/game/app to bad porn site etc.. – So check your household/family members to see what they were/are doing, and in my case – I will be conducting an interview with my employees.

    Good Luck!


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