The article covers must-know facts about Cryptolocker, an advanced persistent Trojan that applies uncrackable RSA cipher to encode victims’ data.
It has been around three years since the first fully functional instances of encryption-based ransomware emerged. The threat landscape has changed considerably over this period, but some infections from this cluster stay and still thrive. The malicious program known as Cryptolocker typifies such an inviolability. Although it has gone through several critical ups and downs, its recurrent iterations never failed to hit the headlines due to the invariably large attack surface, unbeatable cryptographic grip on infected users’ personal files, and high success rate of payload serving. The way this crimeware deploys encryption is tricky as it actually leverages an amalgam of RSA and AES, thus leaving hardly any data recovery options for the assaulted person other than paying the ransom.
Incidentally, the recent edition of Cryptolocker mentions RSA-4096 asymmetric cipher on its warning screen, but this isn’t quite true. The entropy is in fact smaller as the keys are 2048 bits long, but it’s still enough to make the decryption vector of file recovery efforts null and void. Anyway, it takes this ransomware some time before it gets down to the crypto job proper. The first thing it does on a contaminated Windows computer is it adjusts the work of the host system in its own way by adding autostart values and disabling VSS (Volume Shadow Copy Service) to prevent easy file restoration. The next stage is a scan of all letter volumes both on the hard drive and the adjacent network if any. Unmapped network shares are not at risk.
Once the list of the victim’s personal files has been compiled, Cryptolocker triggers the encryption routine and makes them inaccessible. Some versions of the malware contort the appearance of files by modifying the filenames and adding bizarre extensions. It’s only at this point that the Trojan notifies the user of the attack. It displays a UI with a warning message and configures an image with ransom instructions to replace the original desktop wallpaper. According to the notifications, the victim has to pay 0.5-1 Bitcoin during 72 hours. The payment processing service is built into the program’s pane, so the person can navigate back and forth using the toggles provided.
Should the ransom not be submitted in time, the extortionists threaten the target to erase the private decryption key from their Command & Control server. In plain language, this means that the data will remain locked for good. Under certain circumstances, though, it may be possible to reanimate some files through the use of specially crafted recovery tools. Furthermore, Shadow Copies of some items may not be lost if the ransomware has failed to terminate the respective service. All in all, there might be a little bit of chance for remediation.
Automated removal of Cryptolocker ransomware
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.
Cryptolocker 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 Cryptolocker 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 file recovery
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 Cryptolocker 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.