4k Ransomware

Also Known As: 4k virus
Distribution: Moderate
Damage level: Severe

4k ransomware removal instructions

What is 4k?

4k is the name of a ransomware-type program which is designed to blackmail victims by encrypting their data and forcing them to pay a ransom. It was discovered by by Jakub Kroustek and it is a part of other ransomware's family which is called Dharma. 4k changes every file's name by adding the ".4k" extension to it. it also adds the victim's ID and email address of cyber criminals who developed it. For example, 4k renames "1.jpg" to "1.jpg.id-1E857D00.[rocosmon@cock.li].4k" and so on. It generates two ransom notes: one in a pop-up window and another one in the "RETURN FILES.txt" file.

The text file says that all victim's files are encrypted and they can be recovered by contacting cyber criminals who designed it via rocosmon@cock.li. The pop-up window contains more details. It says that 4k encrypted files with RSA-1024 encryption, to restore/decrypt them, victims are encouraged to contact 4k's developers via the same email address that is provided in the "RETURN FILES.txt" file. However, this pop-up window says that it should be done in 7 days after encryption because later decryption keys might be overwritten and victims will not be able to decrypt their files anymore. It is unknown what is the price of a decryption tool/key, however, it should be named after 4k's developers are contacted. Most cyber criminals ask to be paid in cryptocurrency (like Bitcoins). Cyber criminals who developed this ransomware promise to send decryption tool, keys and instructions on how to use them right after the payment. They even offer a free decryption of one file that can be sent to them via the email before making a payment. Nevertheless, even if they have the right decryption tool, they should not be trusted. Most ransomware developers to not send their victims tools that supposed to help them to decrypt encrypted files. Once they get the money/cryptocurrency, they do not reply their victims or send them decryption tools/keys that they promised to send. This is the main reason why we do not recommend to contact or pay any cyber criminals/ransomware developers. Unfortunately, there is not tool that could be capable of decrypting 4k's encryption for free. The only way to recover files without having to contact cyber criminals is to restore everything from a data backup.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:

4k decrypt instructions

4k shares similarities with other ransomware-type programs of this type like PLUT, Jack, DDOS and a great number of others. Most of the times such malware is designed to encrypt files and to display ransom notes/force people to buy tools requited for a decryption. Main differences usually are price of the decryption and cryptography algorithm that is used to perform the encryption. Biggest trouble is that encryptions causes by ransomware are almost impossible to decrypt without interference of cyber criminals (without using tools that only they have). It is possible only in cases when ransomware-type programs are not fully developed, have some bugs, flaws and so on. To avoid data (and financial) loss, we recommend to always have a backup created and to keep it stored on remote server or unplugged storage devices.

How did ransomware infect my computer?

Cyber criminals could be spreading malicious in various ways. However, most of the times they do it using spam campaigns (emails), software 'cracking' tools, trojans, unreliable software download channels and unofficial software updaters. One of the most common ways to trick people into infecting their computers is to send emails that contain malicious attachments. When people open them, they allow those files to download and install malware. Some examples of attachments that cyber criminals send are Microsoft Office documents, executables, PDF documents, archive files like ZIP, RAR, JavaScript files and so on. Software activations performed using 'cracking' tools can lead to installations of high-risk viruses. Programs of this type are often used to spread malware and do not operate as they supposed to. Trojans can be used to proliferate malware too. These are programs that usually are designed to cause chain infections/spread other malicious software. Peer-to-peer networks (such as torrents, eMule and so on), third party downloaders/installers, freeware download websites or file hosting websites can be used to infect computers by presenting malicious files as legitimate. By downloading and opening them unsuspecting people install computer infections by themselves. If used, fake software updaters either exploit bugs or flaws of the installed software or download and install malicious programs instead installing updates or fixes.

Threat Summary:
Name 4k virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .4k (this ransomware also appends filenames with victim's unique ID and developers' email address).
Ransom Demanding Message Pop-up window, RETURN FILES.txt text file.
Cyber Criminal Contact rocosmon@cock.li
Detection Names (p.exe) Avast (Win32:Malware-gen), BitDefender (Trojan.Ransom.Crysis.E), ESET-NOD32 (a variant of Win32/Filecoder.Crysis.P), Kaspersky (Trojan-Ransom.Win32.Crusis.to), Full List Of Detections (VirusTotal)
Symptoms Can't open files stored on your computer, previously functional files now have a different extension, for example my.docx.locked. A ransom demanding message is displayed on your desktop. Cyber criminals are asking to pay a ransom (usually in bitcoins) to unlock your files.
Distribution methods Infected email attachments (macros), torrent websites, malicious ads.
Damage All files are encrypted and cannot be opened without paying a ransom. Additional password stealing trojans and malware infections can be installed together with a ransomware infection.

To eliminate 4k virus our malware researchers recommend scanning your computer with Spyhunter.
▼ Download Spyhunter
Free scanner checks if your computer is infected. To remove malware, you have to purchase the full version of Spyhunter.

How to protect yourself from ransomware infections?

We recommend to be careful with attachments (or links) presented in irrelevant emails that are received from unknown, dubious addresses. Very often these emails are presented as official, however, they should not be trusted. Furthermore, the safest way to download any software (especially if it is free) is using official websites. Tools that we mentioned in the paragraph above should not be used for that. Same applies to software updates: it is important to update installed software using tools (or functions) that are provided by official software developers, unofficial tools might infect computers. If some software requires activation, do not use 'cracking' to bypass it. Usage of such tools is a cyber crime and might lead to downloads and installations of malware too. And finally, it is not recommended to use operating system and browse the web without anti-virus or anti-spyware suite installed and enabled. If your computer is already infected with 4k, we recommend running a scan with Spyhunter for Windows to automatically eliminate this ransomware.

Text presented in 4k ransomware's text file:

You can send us up to 1 file for free decryption. The total size of files must be less than 1Mb (non archived), and files should not contain valuable information. (databases,backups, large excel sheets, etc.)
When you make sure of decryption possibility transfer the money to our bitcoin wallet. As soon as we receive the money we will send you:
1. Decryption program.
2. Detailed instruction for decryption.
3. And individual keys for decrypting your files.
Do not rename encrypted files.
Do not try to decrypt your data using third party software, it may cause permanent data loss.
Decryption of your files with the help of third parties may cause increased price (they add their fee to our) or you can become a victim of a scam.

Screenshot of 4k's text file ("RETURN FILES"):

4k text file

Screenshot of 4k's text file:

All your data is encrypted!
for return write to mail:

Screenshot of files encrypted by 4k (".4k" extension):

Files encrypted by 4k

4k ransomware removal:

Instant automatic removal of 4k virus: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Spyhunter is a professional automatic malware removal tool that is recommended to get rid of 4k virus. Download it by clicking the button below:
▼ DOWNLOAD Spyhunter By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. Free scanner checks if your computer is infected. To remove malware, you have to purchase the full version of Spyhunter.

Quick menu:

Step 1

Windows XP and Windows 7 users: Start your computer in Safe Mode. Click Start, click Shut Down, click Restart, click OK. During your computer start process, press the F8 key on your keyboard multiple times until you see the Windows Advanced Option menu, and then select Safe Mode with Networking from the list.

Safe Mode with Networking

Video showing how to start Windows 7 in "Safe Mode with Networking":

Windows 8 users: Start Windows 8 is Safe Mode with Networking - Go to Windows 8 Start Screen, type Advanced, in the search results select Settings. Click Advanced startup options, in the opened "General PC Settings" window, select Advanced startup. Click the "Restart now" button. Your computer will now restart into the "Advanced Startup options menu". Click the "Troubleshoot" button, and then click the "Advanced options" button. In the advanced option screen, click "Startup settings". Click the "Restart" button. Your PC will restart into the Startup Settings screen. Press F5 to boot in Safe Mode with Networking.

Windows 8 Safe Mode with networking

Video showing how to start Windows 8 in "Safe Mode with Networking":

Windows 10 users: Click the Windows logo and select the Power icon. In the opened menu click "Restart" while holding "Shift" button on your keyboard. In the "choose an option" window click on the "Troubleshoot", next select "Advanced options". In the advanced options menu select "Startup Settings" and click on the "Restart" button. In the following window you should click the "F5" button on your keyboard. This will restart your operating system in safe mode with networking.

windows 10 safe mode with networking

Video showing how to start Windows 10 in "Safe Mode with Networking":

Step 2

Log in to the account infected with the 4k virus. Start your Internet browser and download a legitimate anti-spyware program. Update the anti-spyware software and start a full system scan. Remove all entries detected.

If you cannot start your computer in Safe Mode with Networking, try performing a System Restore.

Video showing how to remove ransomware virus using "Safe Mode with Command Prompt" and "System Restore":

1. During your computer start process, press the F8 key on your keyboard multiple times until the Windows Advanced Options menu appears, and then select Safe Mode with Command Prompt from the list and press ENTER.

Boot your computer in Safe Mode with Command Prompt

2. When Command Prompt mode loads, enter the following line: cd restore and press ENTER.

system restore using command prompt type cd restore

3. Next, type this line: rstrui.exe and press ENTER.

system restore using command prompt rstrui.exe

4. In the opened window, click "Next".

restore system files and settings

5. Select one of the available Restore Points and click "Next" (this will restore your computer system to an earlier time and date, prior to the 4k ransomware virus infiltrating your PC).

select a restore point

6. In the opened window, click "Yes".

run system restore

7. After restoring your computer to a previous date, download and scan your PC with recommended malware removal software to eliminate any remaining 4k ransomware files.

To restore individual files encrypted by this ransomware, try using Windows Previous Versions feature. This method is only effective if the System Restore function was enabled on an infected operating system. Note that some variants of 4k are known to remove Shadow Volume Copies of the files, so this method may not work on all computers.

To restore a file, right-click over it, go into Properties, and select the Previous Versions tab. If the relevant file has a Restore Point, select it and click the "Restore" button.

Restoring files encrypted by CryptoDefense

If you cannot start your computer in Safe Mode with Networking (or with Command Prompt), boot your computer using a rescue disk. Some variants of ransomware disable Safe Mode making its removal complicated. For this step, you require access to another computer.

To regain control of the files encrypted by 4k, you can also try using a program called Shadow Explorer. More information on how to use this program is available here.

shadow explorer screenshot

To protect your computer from file encryption ransomware such as this, use reputable antivirus and anti-spyware programs. As an extra protection method, you can use programs called HitmanPro.Alert and EasySync CryptoMonitor, which artificially implant group policy objects into the registry to block rogue programs such as 4k ransomware.

Note that Windows 10 Fall Creators Update includes "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default this feature automatically protects files stored in Documents, Pictures, Videos, Music, Favorites as well as Desktop folders.

Controll Folder Access

Windows 10 users should install this update to protect their data from ransomware attacks. Here's more information on how to get this update and add additional protection layer from ransomware infections.

HitmanPro.Alert CryptoGuard - detects encryption of files and neutralises any attempts without need for user-intervention:

hitmanproalert ransomware prevention application

Malwarebytes Anti-Ransomware Beta uses advanced proactive technology that monitors ransomware activity and terminates it immediately - before reaching users' files:

malwarebytes anti-ransomware

  • The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups. More information on online backup solutions and data recovery software Here.

Other tools known to remove 4k ransomware: