Cat4er Ransomware


Cat4er is one of the newest Ransomware viruses. If your PC has been compromised by Cat4er, you will notice that your files have become inaccessible.


The Cat4er ransomware will leave a HOW_FIX_FILES.htm with instructions

Ransomware is considered among the most notorious of all online threats, but our manual guide will allow you to remove it from your system as soon as possible. As far as the encrypted files are concerned, we have prepared a potential workaround, and added it to the same guide, but we cannot guarantee that all of your data can be recovered. In fact, this is one of the main reasons why the Ransomware infections are considered to be so harmful.

This software is developed to compromise the user’s computer by stealth, and silently encrypt the files there with the help of a complex algorithm. The encryption that gets applied results in the modification of the file extensions, which renders them unreadable to any software present on the computer, thus making them unavailable to the user. The malicious software then places a ransom notification on the victim’s monitor, once the encryption is done. This note typically requires a ransom payment, and includes instructions related to the payment method, which typically involves purchasing BitCoins and sending them to the hacker’s virtual wallet. The hackers who control the Ransomware promise to send to the victims a special decryption key once the payment is made – the said key is necessary in order to unlock the encrypted files.

The Cat4er virus

The Cat4er virus is used for blackmailing its victims. The people who have been attacked by the Cat4er virus will notice a ransom note on their screen.

Cat4er virus

The Cat4er virus encrypted files

There are many commonly used techniques that prove effective in spreading infections like Cat4er, Nqhd, Miia to different devices. One of the most popular ones is the method of malvertising. Malvertisements are ads in different shapes and sizes (banners, popups, etc.) that have been loaded with a malicious script, which activates after clicking on the ad. The advertisements may be specifically designed for this purpose, or they may be actual advertisements for legitimate products or services that have been compromised by criminals. That’s why it is very important that you are always on the lookout for online advertising materials, and why you should avoid clicking on random pop-up messages.

Additionally, the hackers who create threats like Cat4er oftentimes use online download portals, different obscure file-sharing sites, and torrent sites. You are more likely to get an infection from such a website than from any other online location. Ransomware like Cat4er may also often be distributed in software installers, which are bundled with two or more programs (files). Another distribution strategy is using a Trojan that can insert the Ransomware into the already infected system. Such a malware could be sent to you as an attachment to a spam email, that could be disguised as a legit message. Once the infected attachment gets opened, the Trojan will automatically activate in your computer and begin the process of downloading the Ransomware. Unfortunately, most of those distribution techniques don’t trigger any overly-evident symptoms, which is why you will most likely have no reason to suspect that you have been compromised until you notice the ransom-demanding notification.

The Cat4er file encryption

The Cat4er file encryption is a data-locking process. Once completed, the Cat4er file encryption process will make your files inaccessible without the application of a corresponding decryption key.

Security experts, however, advise the victims of Cat4er to not get panicked, and to refrain from paying the ransom for the decryption key immediately. Instead, they recommend exploring alternative methods that can remove the Ransomware, and get some of the files back without the payment of a ransom.


Name Cat4er
Type Ransomware
Danger Level High (Ransomware is by far the worst threat you can encounter)
Data Recovery Tool Not Available
Detection Tool

Remove Cat4er Ransomware


Some of the steps will likely require you to exit the page. Bookmark it for later reference.

Reboot in Safe Mode (use this guide if you don’t know how to do it).



Press CTRL + SHIFT + ESC at the same time and go to the Processes Tab. Try to determine which processes are dangerous. 


Right click on each of them and select Open File Location. Then scan the files with our free online virus scanner:

Each file will be scanned with up to 64 antivirus programs to ensure maximum accuracy
This scanner is free and will always remain free for our website's users.
This file is not matched with any known malware in the database. You can either do a full real-time scan of the file or skip it to upload a new file. Doing a full scan with 64 antivirus programs can take up to 3-4 minutes per file.
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    After you open their folder, end the processes that are infected, then delete their folders. 

    Note: If you are sure something is part of the infection – delete it, even if the scanner doesn’t flag it. No anti-virus program can detect all infections.


    Hold the Start Key and R –  copy + paste the following and click OK:

    notepad %windir%/system32/Drivers/etc/hosts

    A new file will open. If you are hacked, there will be a bunch of other IPs connected to you at the bottom. Look at the image below:

    hosts_opt (1)

    If there are suspicious IPs below “Localhost” – write to us in the comments.

    Type msconfig in the search field and hit enter. A window will pop-up:


    Go in Startup —> Uncheck entries that have “Unknown” as Manufacturer.

    • Please note that ransomware may even include a fake Manufacturer name to its process. Make sure you check out every process here is legitimate.


    Type Regedit in the windows search field and press EnterOnce inside, press CTRL and F together and type the virus’s Name. 

    Search for the ransomware  in your registries and delete the entries. Be extremely careful –  you can damage your system if you delete entries not related to the ransomware.

    Type each of the following in the Windows Search Field:

    1. %AppData%
    2. %LocalAppData%
    3. %ProgramData%
    4. %WinDir%
    5. %Temp%

    Delete everything in Temp. The rest just check out for anything recently added. Remember to leave us a comment if you run into any trouble!


    How to Decrypt Cat4er files

    We have a comprehensive (and daily updated) guide on how to decrypt your files. Check it out here.

    If the guide doesn’t help, download the anti-virus program we recommended or try our free online virus scanner. Also, you can always ask us in the comments for help!

    About the author


    Lidia Howler

    Lidia is a web content creator with years of experience in the cyber-security sector. She helps readers with articles on malware removal and online security. Her strive for simplicity and well-researched information provides users with easy-to-follow It-related tips and step-by-step tutorials.

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