Home Guides How to decrypt .ykcol virus files – Ykcol/Locky ransomware

How to decrypt .ykcol virus files – Ykcol/Locky ransomware

5 min read
A fresh update of the Locky ransomware has brought about several changes, including the .ykcol extension being affixed to files, and ykcol.htm/ykcol.bmp rescue notes.

Locky, one of the heavyweights on the online extortion arena, has undergone another major tweak. Its latest edition is referred to as Ykcol based on the new file extension token and the names of data decryption how-to manuals added to a contaminated system. Meanwhile, this variant shares most of its properties with the predecessor dubbed Lukitus. In particular, it is being distributed via malicious spam carrying a trojanized file on board. These emails may be camouflaged as invoice notifications and are typically titled “Status of invoice”. Note that this is merely one of the spam waves reportedly involved in Locky distribution at this point, so other phishing themes are most likely to surface as well. Regardless of the subject, the attached ZIP archive has a malicious VBS file inside. When opened, this entity automatically downloads the Ykcol binary onto the target computer behind the scenes.

Files with the .ykcol extension plus ransom note by Ykcol/Locky virus
Files with the .ykcol extension plus ransom note by Ykcol/Locky virus

As soon as the payload has been executed, it traverses the host for potentially important data. To this end, it scans hard drive partitions, removable repositories such as USB memory sticks, and network drives in search of files with specific extensions matching popular formats. Every spotted item is subject to rock-solid encryption. The Ykcol/Locky ransomware leverages a combination of two ciphers, RSA-2048 and AES-128, to render victims’ valuable data inaccessible. The aftermath of this skewing routine is a severe modification of filenames. They turn into long strings consisting of 36 hexadecimal characters followed by the above-mentioned .ykcol string. For instance, a file originally named Cat.jpg will morph into something like this: IZ7FDG12-KQ76-ITX5-AF3819CF-55DCDC930421.ykcol.

Ykcol.bmp rescue note used to replace desktop wallpaper
Ykcol.bmp rescue note used to replace desktop wallpaper

To let the victim know what’s going on and how to act, the Ykcol virus creates recovery how-to manuals named ykcol.htm and ykcol.bmp. These may assume an alternate shape like ykcol-[4 chars].htm/bmp. The former is dropped on the desktop and sprinkled across folders with hostage data. The latter edition (BMP file) is used to replaces the user-defined desktop background with some warning text conveying basic restoration steps. Both say the following, “!!! IMPORTANT INFORMATION !!!! All of your files are encrypted with RSA-2048 and AES-128 ciphers.” Then goes a part reading, “Decrypting of your files is only possible with the private key and decrypt program, which is on our secret server.

Ultimately, the victim is pressured into visiting a specially crafted Tor resource titled the Locky Decryptor Page. This page, incidentally, has been invariable throughout Locky’s existence, with the only volatile part being the size of the ransom. In the case of the Ykcol ransomware, the amount is 0.25 Bitcoin. The page provides the Bitcoin wallet address to submit the ransom, and contains a field for the decryptor download link which will supposedly become available once the payment has been verified. A huge caveat in fighting all iterations of Locky is that the crypto is too strong to brute force or otherwise get around. So backups pose the best response to such attacks. If there are none, it’s worthwhile trying a few forensic techniques listed below.

Ykcol 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

Download Ykcol virus remover

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 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

Ykcol 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 Ykcol 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 Ykcol ransomware using Safe Mode with Networking

Remove Ykcol ransomware using Safe Mode with Networking

Get rid of Ykcol ransomware using System Restore

Get rid of Ykcol 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 .ykcol 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 Ykcol 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 Ykcol 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 Ykcol ransomware removal tool

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