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COSW Virus Ransomware [.cosw Files] Remove and Decrypt Guide

What Is Cosw Virus?

Cosw ransomware is a type of malicious software from the STOP/DJVU family that targets Microsoft Windows operating systems. It encrypts files on the infected computer and adds the .Cosw virus file extension to them. Victims are then presented with a ransom note, demanding payment to receive the decryption key and unlock the encrypted files. Victims are warned that if they do not pay the ransom within a predetermined time frame, their files will be deleted permanently.

Cosw Virus – Why Is My Windows Infected?

The most prevalent mechanism of acquiring Cosw virus ransomware is through opening obfuscated attachments included in emails or hidden files downloaded from malevolent websites. Other techniques of contagion include downloading software with malware enfolded within it, browsing shady websites, or by taking advantage of security flaws in the operating system or other software.

Cosw virus files removal decryptor free COSW Virus Ransomware [.cosw Files] Remove and Decrypt Guide

Cosw Virus – How Did I Get Infected?

The main ways Cosw virus ransomware is typically spread include malicious emails and websites, malicious software downloads, and exploiting security vulnerabilities in the operating system or other software. The following means of distribution are the main ones usually used:

  • If it is sent to you as an e-mail attachment or a URL.
  • By being downloaded from a shady site.

Cosw Virus – What Does It Do?

Once the virus has infiltrated your computer, it will start scrambling your files. It will then present you with a demand for payment in return for a code that will unlock the encrypted files. Generally, the ransom note will warn that the files will be permanently erased if the ransom is not paid before a certain date.

The payload files of the virus may be created in the following Windows directories:

  • %Local%
  • %Temp%
  • %Windows%
  • %SystemDrive%
  • %LocalLow%
  • %AppData%
  • %System%
  • %system32%

If your device has been infected by this virus, it may leave a ransom note, called _readme.txt, with the following content:

STOP ransomware virus ransom message

The virus has been known to insert its value entries into multiple Windows Registries as one of its activities.

Cosw Virus – Details

Name Cosw virus, also known as UDS:Trojan.Win32.Chapak.gen, Ransom:Win32/StopCrypt.KM!MTB, Win32:PWSX-gen [Trj], Win32:PWSX-gen [Trj], A Variant Of Win32/GenKryptik.FHJB – more detections of this virus on VirusTotal
File Extension .cosw
Type Ransomware, Cryptovirus
Short Description The ransomware encrypts files on your computer system and demands a ransom to be paid to allegedly recover them.
Symptoms The Cosw Virus ransomware will encrypt your files by appending the .cosw extension to them.
Ransom Demanding Note _readme.txt
Distribution Method Spam Emails, Email Attachments
Detection Tool See If Your Mac Has Been Affected by Cosw

Download

Malware Removal Tool

What Are .cosw Files

Files with the .cosw virus file extension have been encrypted by this ransomware virus using the AES encryption algorithm, making them unusable until the encryption is reversed. To restore access to the files, one must either pay the ransom or utilize a dependable data recovery tool.

  • Videos (.mp4, .avi, etc.).
  • Audio (.mp3, .wav, etc.).
  • Picture file kinds (.jpg, .png, .etc).
  • Archive file formats (.zip, .rar, etc).
  • Documents of different types (.docx, .pptx, etc.).
  • Others.

cosw files removal file extension virus decryption guide

Picture.jpg.cosw

How to Open .cosw Files

Unfortunately, there is no way to access .cosw virus ransomware files without paying the ransom demanded by the perpetrators. If your files have been encrypted by DJVU ransomware, the best course of action is to concentrate on eliminating the malicious virus from your system and recovering your files from a backup.

What To Do If My Files Are .cosw?

If you have been affected by Cosw virus ransomware and its cipher and need to recover your files, one of the most reliable thigs to do so is to restore them from a backup. In the absence of a backup, you may attempt to retrieve your data using data recovery software, as instructed in the guide linked below. Please be aware that these solutions may not always be effective as the files are encrypted.

How To Protect Windows from Cosw In The Future?

In order to safeguard your Windows system from the Cosw virus ransomware, it is essential to keep your system up-to-date with the most recent security patches and updates, know how to safely store your files to protect them from ransomware, be vigilant when browsing websites, and be cautious of what files you download.

How to Remove Cosw Virus?

To protect your computer from further encryption and recover any encrypted files, you should first disconnect your machine from the internet to prevent the Cosw virus ransomware from spreading. Next, use a reliable anti-malware program to scan your device and remove the malicious files associated with the ransomware. If you have backed up your files, you can easily restore them from the backup. If not, you can attempt to use data recovery tools to try and recover the encrypted files.

How to Decrypt / Fix .cosw Files?

To decrypt files that have been encrypted by this virus, we recommend that you follow the STOP Ransomware decryption steps. These steps include the use of a decryption tool, which was developed by independent researchers to help victims of the virus and finds your decryption key.

Ventsislav Krastev

Ventsislav is a cybersecurity expert at SensorsTechForum since 2015. He has been researching, covering, helping victims with the latest malware infections plus testing and reviewing software and the newest tech developments. Having graduated Marketing as well, Ventsislav also has passion for learning new shifts and innovations in cybersecurity that become game changers. After studying Value Chain Management, Network Administration and Computer Administration of System Applications, he found his true calling within the cybersecrurity industry and is a strong believer in the education of every user towards online safety and security.

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  • Step 1
  • Step 2
  • Step 3
  • Step 4
  • Step 5

Step 1: Scan for Cosw with SpyHunter Anti-Malware Tool

1. Click on the "Download" button to proceed to SpyHunter's download page.


It is recommended to run a scan before purchasing the full version of the software to make sure that the current version of the malware can be detected by SpyHunter. Click on the corresponding links to check SpyHunter's EULA, Privacy Policy and Threat Assessment Criteria.


2. After you have installed SpyHunter, wait for it to update automatically.

scan for and delete ransomware virus step 2


3. After the update process has finished, click on the 'Malware/PC Scan' tab. A new window will appear. Click on 'Start Scan'.

scan for and delete ransomware virus step 3


4. After SpyHunter has finished scanning your PC for any files of the associated threat and found them, you can try to get them removed automatically and permanently by clicking on the 'Next' button.

scan for and delete ransomware virus step 4

If any threats have been removed, it is highly recommended to restart your PC.

Ransomware Automatic Removal - Video Guide

Step 2: Uninstall Cosw and related malware from Windows

Here is a method in few easy steps that should be able to uninstall most programs. No matter if you are using Windows 10, 8, 7, Vista or XP, those steps will get the job done. Dragging the program or its folder to the recycle bin can be a very bad decision. If you do that, bits and pieces of the program are left behind, and that can lead to unstable work of your PC, errors with the file type associations and other unpleasant activities. The proper way to get a program off your computer is to Uninstall it. To do that:


1. Hold the Windows Logo Button and "R" on your keyboard. A Pop-up window will appear.
delete ransomware from windows step 1


2. In the field type in "appwiz.cpl" and press ENTER.
delete ransomware from windows step 2


3. This will open a window with all the programs installed on the PC. Select the program that you want to remove, and press "Uninstall"
delete ransomware from windows step 3Follow the instructions above and you will successfully delete most unwanted and malicious programs.


Step 3: Clean any registries, created by Cosw on your computer.

The usually targeted registries of Windows machines are the following:

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce

You can access them by opening the Windows registry editor and deleting any values, created by Cosw there. This can happen by following the steps underneath:

1. Open the Run Window again, type "regedit" and click OK.
delete ransomware virus registries step 1


2. When you open it, you can freely navigate to the Run and RunOnce keys, whose locations are shown above.
delete ransomware virus registries step 2


3. You can remove the value of the virus by right-clicking on it and removing it.
delete ransomware virus registries step 3 Tip: To find a virus-created value, you can right-click on it and click "Modify" to see which file it is set to run. If this is the virus file location, remove the value.

IMPORTANT!
Before starting "Step 4", please boot back into Normal mode, in case you are currently in Safe Mode.
This will enable you to install and use SpyHunter 5 successfully.

Step 4: Boot Your PC In Safe Mode to isolate and remove Cosw

OFFER

Manual Removal Usually Takes Time and You Risk Damaging Your Files If Not Careful!
We Recommend To Scan Your PC with SpyHunter

Keep in mind, that SpyHunter’s scanner is only for malware detection. If SpyHunter detects malware on your PC, you will need to purchase SpyHunter's malware removal tool to remove the malware threats. Read our SpyHunter 5 review. Click on the corresponding links to check SpyHunter's EULA, Privacy Policy and Threat Assessment Criteria

1. Hold Windows Key + R.
remove ransomware in safe mode step 1


2. The "Run" Window will appear. In it, type "msconfig" and click OK.
remove ransomware in safe mode step 2


3. Go to the "Boot" tab. There select "Safe Boot" and then click "Apply" and "OK".
remove ransomware in safe mode step 3
Tip: Make sure to reverse those changes by unticking Safe Boot after that, because your system will always boot in Safe Boot from now on.


4. When prompted, click on "Restart" to go into Safe Mode.
remove ransomware in safe mode step 4


5. You can recognise Safe Mode by the words written on the corners of your screen.
remove ransomware in safe mode step 5


Step 5: Try to Restore Files Encrypted by Cosw.

Method 1: Use STOP Decrypter by Emsisoft.

Not all variants of this ransomware can be decrypted for free, but we have added the decryptor used by researchers that is often updated with the variants which become eventually decrypted. You can try and decrypt your files using the instructions below, but if they do not work, then unfortunately your variant of the ransomware virus is not decryptable.

Follow the instructions below to use the Emsisoft decrypter and decrypt your files for free. You can download the Emsisoft decryption tool linked here and then follow the steps provided below:

1 Right-click on the decrypter and click on Run as Administrator as shown below:

stop ransomware decryptor step 1

2. Agree with the license terms:

stop ransomware decryptor step 2

3. Click on "Add Folder" and then add the folders where you want files decrypted as shown underneath:

stop ransomware decryptor step 3

4. Click on "Decrypt" and wait for your files to be decoded.

stop ransomware decryptor step 4

Note: Credit for the decryptor goes to Emsisoft researchers who have made the breakthrough with this virus.

Method 2: Use data recovery software

Ransomware infections and Cosw aim to encrypt your files using an encryption algorithm which may be very difficult to decrypt. This is why we have suggested a data recovery method that may help you go around direct decryption and try to restore your files. Bear in mind that this method may not be 100% effective but may also help you a little or a lot in different situations.

1. Download the recommended Data Recovery software by clicking on the link underneath:

Simply click on the link and on the website menus on the top, choose Data Recovery - Data Recovery Wizard for Windows or Mac (depending on your OS), and then download and run the tool.


Cosw-FAQ

What is Cosw Ransomware?

Cosw is a ransomware infection - the malicious software that enters your computer silently and blocks either access to the computer itself or encrypt your files. 

Many ransomware viruses use sophisticated encryption algorithms to make your files inaccessible. The goal of ransomware infections is to demand that you pay a ransom payment to get access to your files back.

What Does Cosw Ransomware Do?

Ransomware in general is a malicious software that is designed to block access to your computer or files until a ransom is paid.

Ransomware viruses can also damage your system, corrupt data and delete files, resulting in the permanent loss of important files.

How Does Cosw Infect?

Via several ways.Cosw Ransomware infects computers by being sent via phishing emails, containing virus attachment. This attachment is usually masked as an important document, like an invoice, bank document or even a plane ticket and it looks very convincing to users.

Another way you may become a victim of Cosw is if you download a fake installer, crack or patch from a low reputation website or if you click on a virus link. Many users report getting a ransomware infection by downloading torrents.

How to Open .Cosw files?

You can't without a decryptor. At this point, the .Cosw files are encrypted. You can only open them once they are decrypted using a specific decryption key for the particular algorithm.

What to Do If a Decryptor Does Not Work?

Do not panic, and backup the files. If a decryptor did not decrypt your .Cosw files successfully, then do not despair, because this virus is still new.

Can I Restore ".Cosw" Files?

Yes, sometimes files can be restored. We have suggested several file recovery methods that could work if you want to restore .Cosw files. 

These methods are in no way 100% guaranteed that you will be able to get your files back. But if you have a backup, your chances of success are much greater.

How To Get Rid of Cosw Virus?

The safest way and the most efficient one for the removal of this ransomware infection is the use a professional anti-malware program.

It will scan for and locate Cosw ransomware and then remove it without causing any additional harm to your important .Cosw files.

Can I Report Ransomware to Authorities?

In case your computer got infected with a ransomware infection, you can report it to the local Police departments. It can help authorities worldwide track and determine the perpetrators behind the virus that has infected your computer.

Below, we have prepared a list with government websites, where you can file a report in case you are a victim of a cybercrime:

Cyber-security authorities, responsible for handling ransomware attack reports in different regions all over the world:

Germany - Offizielles Portal der deutschen Polizei

United States - IC3 Internet Crime Complaint Centre

United Kingdom - Action Fraud Police

France - Ministère de l'Intérieur

Italy - Polizia Di Stato

Spain - Policía Nacional

Netherlands - Politie

Poland - Policja

Portugal - Polícia Judiciária

Greece - Cyber Crime Unit (Hellenic Police)

India - Mumbai Police - CyberCrime Investigation Cell

Australia - Australian High Tech Crime Center

Reports may be responded to in different timeframes, depending on your local authorities.

Can You Stop Ransomware from Encrypting Your Files?

Yes, you can prevent ransomware. The best way to do this is to ensure your computer system is updated with the latest security patches, use a reputable anti-malware program and firewall, backup your important files frequently, and avoid clicking on malicious links or downloading unknown files.

Can Cosw Ransomware Steal Your Data?

Yes, in most cases ransomware will steal your information. It is a form of malware that steals data from a user's computer, encrypts it, and then demands a ransom in order to decrypt it.

In many cases, the malware authors or attackers will threaten to delete the data or publish it online unless the ransom is paid.

Can Ransomware Infect WiFi?

Yes, ransomware can infect WiFi networks, as malicious actors can use it to gain control of the network, steal confidential data, and lock out users. If a ransomware attack is successful, it could lead to a loss of service and/or data, and in some cases, financial losses.

Should I Pay Ransomware?

No, you should not pay ransomware extortionists. Paying them only encourages criminals and does not guarantee that the files or data will be restored. The better approach is to have a secure backup of important data and be vigilant about security in the first place.

What Happens If I Don't Pay Ransom?

If you don't pay the ransom, the hackers may still have access to your computer, data, or files and may continue to threaten to expose or delete them, or even use them to commit cybercrimes. In some cases, they may even continue to demand additional ransom payments.

Can a Ransomware Attack Be Detected?

Yes, ransomware can be detected. Anti-malware software and other advanced security tools can detect ransomware and alert the user when it is present on a machine.

It is important to stay up-to-date on the latest security measures and to keep security software updated to ensure ransomware can be detected and prevented.

Do Ransomware Criminals Get Caught?

Yes, ransomware criminals do get caught. Law enforcement agencies, such as the FBI, Interpol and others have been successful in tracking down and prosecuting ransomware criminals in the US and other countries. As ransomware threats continue to increase, so does the enforcement activity.

About the Cosw Research

The content we publish on SensorsTechForum.com, this Cosw how-to removal guide included, is the outcome of extensive research, hard work and our team’s devotion to help you remove the specific malware and restore your encrypted files.


How did we conduct the research on this ransomware?

Our research is based on an independent investigation. We are in contact with independent security researchers, and as such, we receive daily updates on the latest malware and ransomware definitions.

Furthermore, the research behind the Cosw ransomware threat is backed with VirusTotal and the NoMoreRansom project.

To better understand the ransomware threat, please refer to the following articles which provide knowledgeable details.


As a site that has been dedicated to providing free removal instructions for ransomware and malware since 2014, SensorsTechForum’s recommendation is to only pay attention to trustworthy sources.

How to recognize trustworthy sources:

  • Always check "About Us" web page.
  • Profile of the content creator.
  • Make sure that real people are behind the site and not fake names and profiles.
  • Verify Facebook, LinkedIn and Twitter personal profiles.

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