Cuag ransomware (virus) - Decryption Steps Included

Important steps to take before you begin malware removal

File encryption and ransomware infection are two independent processes (although the latter would not be possible without the former). However, it is important to understand that malware performs various changes within a Windows operating system, fundamentally changing the way it works.

IMPORTANT for those without backups! → 
If you attempt to use security or recovery software immediately, you might permanently damage your files, and even a working decryptor then would not be able to save them.

Before you proceed with the removal instructions below, you should copy the encrypted files onto a separate medium, such as USB flash drive or SSD, and then disconnect them from your computer. Encrypted data does not hold any malicious code, so it is safe to transfer to other devices.

The instructions below might initially seem overwhelming and complicated, but they are not difficult to understand as long as you follow each step in the appropriate order. This comprehensive free guide will help you to handle the malware removal and data recovery process correctly.

If you have any questions, comments, or are having troubles with following the instructions, please do not hesitate to contact us via the Ask Us section.

IMPORTANT! →
It is vital to eliminate malware infection from the computer fully before starting the data recovery process, otherwise ransomware might re-encrypt retrieved files from backups repeatedly.

Restore Windows "hosts" file to its original state

Some ransomware might modify Windows hosts file in order to prevent users from accessing certain websites online. For example, Djvu ransomware variants add dozens of entries containing URLs of security-related websites, such as 2-spyware.com. Each of the entries means that users will not be able to access the listed web addresses and will receive an error instead.

Here's an example of “hosts” file entries that were injected by ransomware:

In order to restore your ability to access all websites without restrictions, you should either delete the file (Windows will automatically recreate it) or remove all the malware-created entries. If you have never touched the “hosts” file before, you should simply delete it by marking it and pressing Shift + Del on your keyboard. For that, navigate to the following location:

C:\\Windows\\System32\\drivers\\etc\\

Restore files using data recovery software

Since many users do not prepare proper data backups prior to being attacked by ransomware, they might often lose access to their files permanently. Paying criminals is also very risky, as they might not fulfill the promises and never send back the required decryption tool.

While this might sound terrible, not all is lost – data recovery software might be able to help you in some situations (it highly depends on the encryption algorithm used, whether ransomware managed to complete the programmed tasks, etc.). Since there are thousands of different ransomware strains, it is immediately impossible to tell whether third-party software will work for you.

Therefore, we suggest trying regardless of which ransomware attacked your computer. Before you begin, several pointers are important while dealing with this situation:

• Since the encrypted data on your computer might permanently be damaged by security or data recovery software, you should first make backups of it – use a USB flash drive or another storage.
• Only attempt to recover your files using this method after you perform a scan with anti-malware software.

Install data recovery software

1. Download Data Recovery Pro.
2. Double-click the installer to launch it.
   
3. Follow on-screen instructions to install the software.
4. As soon as you press Finish, you can use the app.
5. Select Everything or pick individual folders where you want the files to be recovered from.
6. Press Next.
7. At the bottom, enable Deep scan and pick which Disks you want to be scanned.
8. Press Scan and wait till it is complete.
9. You can now pick which folders/files to recover – don't forget you also have the option to search by the file name!
10. Press Recover to retrieve your files.

Create data backups to avoid file loss in the future

One of the many countermeasures for home users against ransomware is data backups. Even if your Windows get corrupted, you can reinstall everything from scratch and retrieve files from backups with minimal losses overall. Most importantly, you would not have to pay cybercriminals and risk your money as well.

Therefore, if you have already dealt with a ransomware attack, we strongly advise you to prepare backups for future use. There are two options available to you:

• Backup on a physical external drive, such as a USB flash drive or external HDD.
• Use cloud storage services.

The first method is not that convenient, however, as backups need to constantly be updated manually – although it is very reliable. Therefore, we highly advise choosing cloud storage instead – it is easy to set up and efficient to sustain. The problem with it is that storage space is limited unless you want to pay for the subscription.

Using Microsoft OneDrive

OneDrive is a built-in tool that comes with every modern Windows version. By default, you get 5 GB of storage that you can use for free. You can increase that storage space, but for a price. Here's how to setup backups for OneDrive:

1. Click on the OneDrive icon within your system tray.
2. Select Help & Settings > Settings.
   
   
3. If you don't see your email under the Account tab, you should click Add an account and proceed with the on-screen instructions to set yourself up.
   
4. Once done, move to the Backup tab and click Manage backup.
   
   
5. Select Desktop, Documents, and Pictures, or a combination of whichever folders you want to backup.
6. Press Start backup.
   

After this, all the files that are imported into the above-mentioned folders will be automatically backed for you. If you want to add other folders or files, you have to do that manually. For that, open File Explorer by pressing Win + E on your keyboard, and then click on the OneDrive icon. You should drag and drop folders you want to backup (or you can use Copy/Paste as well).

Using Google Drive

Google Drive is another great solution for free backups. The good news is that you get as much as 15GB for free by choosing this storage. There are also paid versions available, with significantly more storage to choose from.

You can access Google Drive via the web browser or use a desktop app you can download on the official website. If you want your files to be synced automatically, you will have to download the app, however.

1. Download the Google Drive app installer and click on it.
   
2. Wait a few seconds for it to be installed.
3. Now click the arrow within your system tray – you should see Google Drive icon there, click it once.
   
4. Click Get Started.
5. Enter all the required information – your email/phone, and password.
6. Now pick what you want to sync and backup. You can click on Choose Folder to add additional folders to the list.
7. Once done, pick Next.
8. Now you can select to sync items to be visible on your computer.
9. Finally, press Start and wait till the sync is complete. Your files are now being backed up.

Report the incident to your local authorities

Ransomware is a huge business that is highly illegal, and authorities are very involved in catching malware operators. To have increased chances of identifying the culprits, the agencies need information. Therefore, by reporting the crime, you could help with stopping the cybercriminal activities and catching the threat actors. Make sure you include all the possible details, including how did you notice the attack, when it happened, etc. Additionally, providing documents such as ransom notes, examples of encrypted files, or malware executables would also be beneficial.

Law enforcement agencies typically deal with online fraud and cybercrime, although it depends on where you live. Here is the list of local authority groups that handle incidents like ransomware attacks, sorted by country:

• USA – Internet Crime Complaint Center IC3
• United Kingdom – ActionFraud
• Canada – Canadian Anti-Fraud Centre
• Australia – ScamWatch
• New Zealand – ConsumerProtection
• Germany – Polizei
• France – Ministère de l'Intérieur

If your country is not listed above, you should contact the local police department or communications center.

Manual removal using Safe Mode

Important! →
Manual removal guide might be too complicated for regular computer users. It requires advanced IT knowledge to be performed correctly (if vital system files are removed or damaged, it might result in full Windows compromise), and it also might take hours to complete. Therefore, we highly advise using the automatic method provided above instead.

Step 1. Access Safe Mode with Networking

Manual malware removal should be best performed in the Safe Mode environment. 

Windows 7 / Vista / XP

1. Click Start > Shutdown > Restart > OK.
2. When your computer becomes active, start pressing F8 button (if that does not work, try F2, F12, Del, etc. – it all depends on your motherboard model) multiple times until you see the Advanced Boot Options window.
3. Select Safe Mode with Networking from the list.

Windows 10 / Windows 8

1. Right-click on Start button and select Settings.
   
   
2. Scroll down to pick Update & Security.
   
3. On the left side of the window, pick Recovery.
4. Now scroll down to find Advanced Startup section.
5. Click Restart now.
   
6. Select Troubleshoot.
7. Go to Advanced options.
8. Select Startup Settings.
9. Press Restart.
10. Now press 5 or click 5) Enable Safe Mode with Networking.

Step 2. Shut down suspicious processes

Windows Task Manager is a useful tool that shows all the processes running in the background. If malware is running a process, you need to shut it down:

1. Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
2. Click on More details.
   
3. Scroll down to Background processes section, and look for anything suspicious.
4. Right-click and select Open file location.
   
5. Go back to the process, right-click and pick End Task.
   
6. Delete the contents of the malicious folder.

Step 3. Check program Startup

1. Press Ctrl + Shift + Esc on your keyboard to open Windows Task Manager.
2. Go to Startup tab.
3. Right-click on the suspicious program and pick Disable.
   
   

Step 4. Delete virus files

Malware-related files can be found in various places within your computer. Here are instructions that could help you find them:

1. Type in Disk Cleanup in Windows search and press Enter.
   
   
2. Select the drive you want to clean (C: is your main drive by default and is likely to be the one that has malicious files in).
3. Scroll through the Files to delete list and select the following:
   

   Temporary Internet Files
   Downloads
   Recycle Bin
   Temporary files

4. Pick Clean up system files.
   
   
5. You can also look for other malicious files hidden in the following folders (type these entries in Windows Search and press Enter):
   

   %AppData%
   %LocalAppData%
   %ProgramData%
   %WinDir%

After you are finished, reboot the PC in normal mode.