CUAG Ransomware. How to decrypt .cuag files?

Written by William Reddy

If you cannot open your photos, documents, or files and also see the .cuag extension on them, your PC is surely infected with Cuag ransomware. It pertains to STOP/Djvu ransomware group

Cuag ransomware ciphers personal documents identified on the victim’s computer with the extension “.cuag” and then creates the ransom note in each folder which contains encrypted files. The instructions are placed on the victim’s desktop in the “readme.txt” file. Its activity is pretty much similar to other examples of the same ransomware family: Avyu, Qqqr, Bbbr.

What is Cuag Ransomware?

NameCuag Virus
Ransomware family1DJVU/STOP2 ransomware
Ransomware note_readme.txt
RansomFrom $490 to $980,
SymptomsThe images, videos, and other documents have the “.cuag” extension and cannot be opened by any programs
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Cuag is file-encrypting ransomware that prevents normal access to your text files, Excel tables, videos and pics by ciphering them. It marks the ciphered] files with the “.cuag” extension. Then Cuag ransomware adds a money ransom note (readme.txt) to each folder. In it, you can see the guidance to pay the ransom ($490-$980 in Bitcoin) to a certain Bitcoin address. The AES-256 or RSA-1028 cipher it utilizes to cipher the files is not decryptable with contemporary computers. Even quantum PCs that already exist will spend thousands of years to get the decryption key.

How dangerous is the Cuag ransomware?

When Cuag ransomware gets on your PC, it will check your system for images, videos, and also important documents. It encrypt] all widespread file formats- .psd, .doc, .docx, .xls, .xlsx, .pdf, .jpeg, .png, et cetera. When these files are found, the ransomware will cipher them and also change their extension to “.cuag” to make sure that you understand what happened.

After the Cuag ransomware ciphered the files on your computer, it will drop the last “readme.txt” file on the desktop. In addition to the ransom payment instructions, the victims also see the emails to contact the cybercriminals – and

Here is the ransom note that the Cuag ransomware shows to its victims:


Don't worry, you can return all your files!
All your files like pictures, databases, documents and other important are encrypted with strongest encryption and unique key.
The only method of recovering files is to purchase decrypt tool and unique key for you.
This software will decrypt all your encrypted files.
What guarantees you have?
You can send one of your encrypted file from your PC and we decrypt it for free.
But we can decrypt only 1 file for free. File must not contain valuable information.
You can get and look video overview decrypt tool:
Price of private key and decrypt software is $980.
Discount 50% available if you contact us first 72 hours, that's price for you is $490.
Please note that you'll never restore your data without payment.
Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours.

To get this software you need write on our e-mail:

Reserve e-mail address to contact us:

How did the Cuag ransomware get on my computer?

The Cuag ransomware spreads by placing links to download hacked programs or games. They keep their eye on all hype subjects which can be chosen to spread ransomware. New games introductions, new popular movies – Cuag creators make everything to get their victims on that. One of the most popular methods these crooks use is one-day websites with torrent downloading links. Nevertheless, pursuing the current trends is not the only way these burglars use. Options that have already turned into standard, such as e-mail spamming, are likewise typical for STOP/Djvu ransomware distribution.

Malicious email spam

The example of email spamming that may lead to Cuag ransomware injection

Preventing this ransomware does not need a lot of effort. Considering the standard rules of computer hygiene will considerably minimize all risks. Keep in mind that starting all documents you get on e-mail is not a good option. Even worse scenario is to allow macros in Microsoft Office documents. But it is much better to stop the malware intrusion at the moment when you have just opened the email message. Checking the sender’s address can say a lot about what you can expect, and also when you see things like “”– it is likely a legit e-mail. Meanwhile, stuff that tries to appear like Amazon or FedEx shipment notification, but uses the e-mail address of “”– must make you get on the alarm. Above, you can see the illustration of such a message.

Outlaw sources of different digital things require some additional description. Going against copyright regulation surely exposes you to the danger of being fined. Nonetheless, using torrent trackers or third-party sites to download “free” programs also exposes you to a wide range of malware. No one can control unidentified people who start the torrent seeding or release the hacked program version on the site with pirated software.

Cuag virus removal instructions.

Download Trojan Killer Portable

Trojan Killer Portable Download

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This guide below shows how to use Trojan Killer Portable3 for Cuag virus detection and removal:

  • STEP 1. Download and install Trojan Killer.

  • STEP 2. Click on "Finish".

  • STEP 3. Wait until necessary updates are downloaded and installed.

  • STEP 4. Select computer scan type.

  • STEP 5. The software will begin scanning your computer.

  • STEP 6. Click on "Cure PC".

Restore the files encrypted by the Cuag ransomware

In most cases, it’s impossible to recover the files encrypted by the Cuag ransomware because the private key needed to unlock the encrypted files is only available through cybercriminals. However, we’ve listed one option you can use to recover your files below.

Warning! Make sure you remove the ransomware from your system first, otherwise, it will repeatedly encrypt your files.

If your files were encrypted with an offline key, there is a chance you can recover them by using Emsisoft Decryptor for the STOP/Djvu decryption tool. Follow the below guide to recover your files using the Emsisoft Decryptor for STOP/Djvu.

  1. You can download Emsisoft Decryptor for STOP Djvu by clicking this link.
  2. When the decryptor has finished downloading, double-click on “decrypt_STOPDjvu.exe” to run this program on your computer.
  3. Click the “Decrypt” button to start the decryption process for Cuag files. The screen will switch to a status view, informing you about your files’ current process and decryption status.
  4. The decryptor will inform you once the decryption process will be finished. If you require the report for your records, you can save it by clicking the “Save log” button.

If the Emsisoft Decryptor can’t decrypt your .cuag files and you do not plan on paying the ransom, it is advised that you make an image of the encrypted drives so that you can decrypt them in the future.

Your computer should now be free of the Cuag ransomware infection. However, suppose your current antivirus allowed this malicious program on your computer. In that case, you might want to consider purchasing the full-featured version of Trojan Killer to protect against these types of threats in the future.

CUAG Ransomware — How To Remove Virus & Decrypt Files?

Name: CUAG Virus

Description: CUAG Virus is a STOP/DJVU family of ransomware-type virus. It encrypts files, video, photos, documents. Encrypted files can be tracked by a specific cuag extension. CUAG ransomware asks victims for a ransom fee about $490 - $980 in Bitcoin.

Offer price: 480

Currency: $

Operating System: Windows

Application Category: Virus

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About the author

William Reddy

I am from Ireland. My parents bought me a computer when I was 11, and several months after I have got a virus on this PC. I decided to enter the INSA Centre Val de Loire university after being graduated from the school. This French educational institution was offering a brand-new cybersecurity course. After getting the master's degree in cybersecurity, I've started working as a virus analyst in a little anti-malware vendor.

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