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.combo ransomware decryptor and removal

6 min read
Numerous files with the .combo extension sprinkled all over a computer are a sign of the CrySiS/Dharma ransomware attack, so learn how to sort things out.

No matter what some computer security analysts may optimistically claim, ransomware is still afloat. This category of malicious code stealthily enters systems, encrypts the most valuable data and won’t undo the harsh impact unless the victim pays up, although there is no certainty that the recovery solution will be provided at the end of the day. The victims deal with criminals, and the latter don’t necessarily carry through with their promises. Zooming out, file-encrypting threats have actually declined by the numbers since last year, but there are prolific strains like CrySiS, or Dharma, that stick around regardless. This particular family is regularly spawning new variants, one of the recent spinoffs being the mod that blemishes encrypted files with the .combo extension.

Encrypted .combo files
Encrypted .combo files

A recognizable quirk of this particular lineage is the way it trespasses on Windows machines. The invariable entry point is via hacked remote desktop services. In other words, the extortionists scan the Internet for open or poorly authenticated RDP connections and then manually drop the harmful entity into the vulnerable systems. As opposed to the overwhelming majority of blackmail viruses, this one reportedly does not involve spam in its distribution mechanisms. Therefore, users who leverage remote connections for whatever purposes are definitely better off applying robust security techniques to prevent easy breach.

As soon as the dangerous binary is in, it invokes a predefined compromise scenario. First, the culprit disables VSS (Volume Snapshot Service) so that the prey cannot restore files from their shadow copies later on. Then, it traverses the hard disk, mapped network drives and removable media for data in specific formats, focusing on the most common extensions that are likely to correlate with important personal files.

FILES ENCRYPTED.txt ransom note by the .combo file virus
FILES ENCRYPTED.txt ransom note by the .combo file virus

Every single match found during the scan is subject to encryption. Unfortunately, the crooks at the helm of the Dharma campaign have gotten the hang of cryptography good enough, so the crypto is strong and properly implemented. The tip of the iceberg is that these files become completely inaccessible and also change on the outside. The get appended with a string composed according to the following pattern: id-[8 random characters].[attacker’s email].combo. For example, a sample item named File1.pdf will turn into something like File1.pdf.id-8421915F.[bitpandacom@qq.com].combo. The email addresses in brackets vary, and some alternative ones include combo@tutanota.de, dcr@airmail.cc, and lok07@tuta.io.

In spite of the fact that the perpetrators’ contact details are a clear clue that the victim should reach out to them for further instructions, the .combo ransomware also provides separate rescue notes in two different formats. One of them is named FILES ENCRYPTED.txt. It says, “All your data has been locked us. You want to return? Write email bitpandacom@qq.com”, where the address, again, is variable. The other edition of ransom notes is named Info.hta. It is launched automatically and provides basically the same instructions, plus includes an option of decrypting up to five files for free. However, relying on the malefactors’ mercy is the wrong tactic. First off, the ransom tends to be at least $1,000 worth of Bitcoin. Secondly, the victims who elect to pay the money leave it all to chance as they won’t be able to claim their decryptor in case the felons refuse to provide it. Anyway, before opting for the ransom be sure to check whether all the other workarounds work.

Use Intego Antivirus for Windows to remove .Combo

Automatic malware removal makes a difference because it ensures exceptional results while saving you a good deal of time. Made by a renowned security provider, Intego Antivirus can detect and delete all files related to .Combo in minutes. In addition to on-demand cleaning, the program will safeguard your PC 24/7 against the latest threats, including browser hijackers, zero-days, ransomware, info-stealers, and more.

Follow these steps to take care of the infection that has stung your Windows machine:

1. Download Intego Antivirus installer.

Download .Combo remover

Download Intego Antivirus installer onto your PC

2. Open the executable file you have just downloaded. This will launch the installation. A series of follow-up screens will walk you through the setup and reflect its progress.Intego Antivirus setup progress

3. When the installation is completed, select Scans in the left-hand sidebar and click Scan now in the “Quick Scan” or “Complete Virus Scan” area, depending on how thoroughly you want Intego Antivirus to check your PC for threats. Be advised that the complete scan takes much more time.Start a scan

4. Wait until the program examines system locations based on the scan mode you have selected. It will keep you informed about the computer area it is currently checking, the time elapsed, the number of files scrutinized, and the threats found so far.Intego Antivirus scan progress

5. Once the scan is over, Intego Antivirus will display a brief summary of the results. Click the Scan Report button to view the details.Scan results overview

6. The report shows in-depth information such as the names of the detected threats, the malware categories they fall into, their location, and the action taken (malicious items are quarantined by default).Detailed scan report

7. To err on the side of caution, click Quarantine in the program’s sidebar, put checkmarks next to the infected files, and click the Delete selected button. Your PC should now be free from malware.Delete quarantined files for good

.Combo 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 .Combo 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 .Combo ransomware using Safe Mode with Networking

Remove .Combo ransomware using Safe Mode with Networking

Get rid of .Combo ransomware using System Restore

Get rid of .Combo 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 .combo 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 .Combo 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 .Combo 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 .Combo removal tool

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