The CryptoMix ransomware strand keeps spewing out new variants, the latest one acting very much like predecessors but appending the .EMPTY extension to files.
It’s hard to think of a crypto malware strand that stays the same over time and doesn’t spawn spinoffs that inherit basic hallmarks of the original infection while adding some novelty with each new iteration. The ransomware environment is becoming increasingly dynamic, so different families of these viruses switch to brand new variants every so often. The codebase referred to as CryptoMix, for example, is far from being a stationary target. It is currently one of the most prolific and frequently updated lineages. Its latest persona uses the .EMPTY file extension to blemish encrypted data and drops rescue notes named _HELP_INSTRUCTION.txt.
The distribution of this CryptoMix mod is backed by a large-scale spam campaign. The deceptive emails are most commonly disguised as payment receipts or invoices and contain ZIP files. Inside these self-extracting archives are JS or VBS objects that automatically download the ransomware binary onto a targeted host.
Next up on the attack chain is a big lookup for data. The EMPTY ransomware variant of CryptoMix scans the infected machine’s hard disk partitions, removable drives if any, and network shares for files with specific extensions. The formats of sought-for information correspond to the most widespread data types, including all image formats, Office documents, PDF files, videos, databases, and many more items that are likely valuable to the victim. The perpetrating program skips operating system related items so that the computer keeps running smooth and the extortion goes unimpeded. When a matching entity is found, the virus encrypts it using symmetric AES cipher. Then, it further encodes the secret AES key with RSA-1024, a strong asymmetric cryptographic standard that cannot be cracked without what’s called the private key.
As it has been mentioned, in addition to the crypto effect the EMPTY/CryptoMix ransomware appends a new extension to every ransomed file. This string is currently set to .EMPTY. Note that the original filenames don’t stay intact and get replaced with 32 hexadecimal characters in the aftermath of the incursion. For example, an entry named Sunrise.bmp becomes something like 522F7C3505BE57F2DB8DD0B20B6F35EC.EMPTY. Obviously, there is absolutely no chance to determine which encrypted file this entry corresponds to.
To keep the victim informed of what happened and how to act, the ransom Trojan creates _HELP_INSTRUCTION.txt ransom notes with payment instructions. Their contents are as follows, “Attention! All your data was encrypted! For specific information, please send us an email with Your ID number: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org. We will help you as soon as possible!” In other words, the crooks tell the victim to contact them via email in order to get ransom payment steps in response. At the end of the day, the infected user will be forwarded to a Tor page designed for submitting ransoms. The latter indicates the amount of Bitcoin to send, as well as the Bitcoin address. The size of the ransom fluctuates and may be anywhere between 0.5 and 1 BTC.
Some EMPTY ransomware victims have reported that the attackers didn’t carry through with their promises after they paid the ransom. So no one can rest assured the hostage files will return to their normal state if the felons’ demands are met. Instead, it’s strongly recommended to give every alternative workaround a shot.
EMPTY/CryptoMix 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
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.
EMPTY 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 .EMPTY 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.
- 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.
- 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.
- 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.
- 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.
- In the Command Prompt window, type cd restore and hit Enter
- Type rstrui.exe in the new command line and press Enter
- 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.
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 .EMPTY 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.
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.
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.
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 EMPTY 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.