CDXX Virus (.cdxx File) Decryption, Removal & Data Restore

Written by Brendan Smith

The Cdxx virus is ransomware of the STOP/Djvu family. This malware is known for file encryption and extortion. When the Cdxx infects a computer, it targets various types of files, like documents, videos, photos, and more. It changes the file structure and adds the “.cdxx” extension to each file, making them inaccessible and unusable without the decryptor.

Cdxx Virus Overview

Cdxx

🤔 Cdxx malware can be classified as ransomware that originates from the DJVU/STOP ransomware family. Its primary purpose is to lock files that are important to you. Then, this ransomware asks its victims to pay the ransom – ($999 – $1999) in Bitcoin.

The Cdxx virus is a malware type that encrypts your files and coerces you into paying for their decryption. This ransomware encrypts various file types. Encrypted files are identifiable by a distinct “.cdxx” extension. The files touched by ransomware become impossible to access and use.

Subsequently, the ransomware demands a ransom payment in Bitcoin from its victims, ranging from $999 to $1999. In all cases, a text file with ransom payment guidances is named as “_readme.txt“.

Cdxx Ransomware operates by Salsa20 encryption algorithms to scramble the contents of the targeted files. Since Cdxx virus employs such a robust encryption method, it becomes particularly difficult, if even possible, to find the decryption key without the assistance of the attackers.

Once Cdxx malware finishes the encryption, it shows a ransom note to the victim, asking for a ransom payment for the decryption key. The ransom note contains instructions on the ways of making the payment and also often includes threats of data loss or increased ransom amounts if the demands are not met within a specified timeframe.

I have created a comprehensive list of the solutions, advice, and practices to neutralize the Cdxx ransomware and recover your files. There are situations when it may be feasible to restore your files, but sometimes, it may be impossible.

Brendan Smith
Brendan Smith
IT Security Expert
First, perform a PC scan using an antivirus tool!
I will assist you in removing the Cdxx virus and guide you through the process of decrypting or restoring encrypted files. Below, you will find several universally applicable methods to recover encrypted .cdxx files. It is crucial to thoroughly read and comprehend the entire set of instructions. Do not skip any steps. Each step is of utmost importance and must be completed by you.
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📌 Important Note!

It is critical to note that paying the ransom does not guarantee the successful files recovery. The rascals who stand behind the Cdxx virus are not trustworthy. There were the cases where people have paid the ransom, only to be denied by the cyber criminals with the decryption key provision.

Cdxx employs a unique key for every victim, with one exception:

  • If Cdxx fails to connect the command and control server (C2) before starting the encryption process, it uses offline keys as a fallback option. An offline key is the same for all users, which allows for the decryption of files encrypted by the ransomware.

The Cdxx virus is highly similar to other DJVU ransomware variants such as Lkhy, Cdpo, Cdwe, and Cdaz. This virus encrypts a wide range of common file types and appends its distinct “.cdxx” extension to all files. For instance, a file named “1.jpg” would be altered to “1.jpg.cdxx” and “2.png” to “2.png.cdxx“.

Upon successful encryption, malware spawns a special text file named “_readme.txt” and places it in every folder containing the encrypted files. It as well adds this file to the desktop, so the user will not miss the attack even without opening folders.

The image below provides a visual representation of files with the “cdxx” extension:

Cdxx Virus - encrypted cdxx files

Encrypted Files by STOP/DJVU Ransomware

Name Cdxx Virus
Ransomware family1 DJVU/STOP2 ransomware
Extension .cdxx
Ransomware note _readme.txt
Ransom From $999 to $1999 (in Bitcoins)
Contact [email protected], [email protected]
Detection Backdoor:Win32/Xtrat.B, Ransom:Win32/Mazedec.TA!MSR, Picsys.Worm.Bot.DDS
Symptoms
  • Encrypted most of your files (photos, videos, documents) and adds a particular “.cdxx” extension;
  • Can delete Volume Shadow copies to make victim’s attempts to restore data impossible;
  • Adds a list of domains to HOSTS file to block access to certain security-related sites;
  • Installs password-stealing Trojan on the system, like Vidar Stealer or RedLine Stealer;
  • Manages to install a SmokeLoader backdoor;
Fix Tool To remove possible malware infections, scan your PC:


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This message asking payment is for restore files via decryption key:

_readme.txt (STOP/DJVU Ransomware)

_readme.txt (STOP/DJVU Ransomware) – The terrifying notification requesting users to pay off the ransom to unlock the encrypted data contains these annoying admonitions.

Cdxx ransomware arrives as a set of tasks that are meant to execute different tasks on a victim’s computer. One of the primary processes being launched is winupdate.exe, a tricky process that displays a fraudulent Windows update prompt during the attack. That is needed to convince the victim that a sudden system slowdown is caused by a Windows update.

Meanwhile, the ransomware runs another process (which name commonly consists of 4 random characters) which commences scanning the computer for target files and encrypting them. Then the ransomware removes Volume Shadow Copies from the system by the following CMD command:

vssadmin.exe Delete Shadows /All /Quiet

Once removed, it becomes nearly impossible to restore the previous computer state using System Restore Points. The issue is, ransomware operators are eliminating any built-in Windows approaches that could aid the victim to recover files for free. In addition, the hackers modify the Windows HOSTS file by adding a list of domains to it and linking them to the localhost IP. As a result, the victim will see a DNS_PROBE_FINISHED_NXDOMAIN error when accessing one of the listed websites.

It has come to our attention that ransomware attempts to block websites that post various how-to guides for computer users. It is obvious that by limiting specific domains, the crooks are attempting to prevent the victim from reaching relevant and helpful ransomware-attack-related information online. Malware also keeps two text files on the victim’s computer that present attack-related details – the victim’s public encryption key and personal ID. These two files are named bowsakkdestx.txt and PersonalID.txt.

Cdxx ransomware virus saves public encryption key and victim's id in bowsakkdestx.txt file

After all these alterations, the malware doesn’t cease. Variants of STOP/DJVU have a tendency to install Vidar password-stealing Trojan on compromised systems. This threat has an large list of capabilities, including:

  • Infiltrating the victim’s computer with malware and executing it to gain unauthorized access.
  • Obtaining unauthorized access to login credentials of Steam, Telegram, and Skype.
  • Manipulating and viewing files on the victim’s computer without their knowledge.
  • Stealing cryptocurrency wallets from the victim’s system.
  • Granting the hackers remote control over the victim’s computer for various malicious activities.
  • Extracting sensitive information such as browser cookies, saved passwords, and browsing history.

The cryptography algorithm in STOP/Djvu ransomware is AES-256. So, once your data is encrypted with an online decryption key, the possibility to get your files back without paying the ransom are quite low. Thing is, the key is unique for each victim, and brute forcing it will take too much time.

Getting the online key in another way is also nearly impossible. It is kept on a command server owned by the criminals who spread the Cdxx malware. For receiving decrypting code the payment should be $1999. To obtain the payment details, the victims should contact the hackers by email ([email protected]).

The message by the ransomware states the following information:

ATTENTION!

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:
https://we.tl/t-FCWSCsjEWS
Price of private key and decrypt software is $1999.
Discount 50% available if you contact us first 72 hours, that's price for you is $999.
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:
[email protected]

Reserve e-mail address to contact us:
[email protected]

Your personal ID:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

How To Remove STOP/Djvu Ransomware?

Remove Cdxx Virus with Gridinsoft Anti-Malware

We have also been using this software on our systems ever since, and it has always been successful in detecting viruses. It has blocked the most common Ransomware as shown from our tests with the software, and we assure you that it can remove Cdxx Virus as well as other malware hiding on your computer.

Gridinsoft Anti-Malware - Main Screen

To use Gridinsoft for remove malicious threats, follow the steps below:

1. Begin by downloading Gridinsoft Anti-Malware, accessible via the blue button below or directly from the official website gridinsoft.com.

2.Once the Gridinsoft setup file (setup-gridinsoft-fix.exe) is downloaded, execute it by clicking on the file.

setup-gridinsoft-fix.exe

3.Follow the installation setup wizard's instructions diligently.

Gridinsoft Setup Wizard

4. Access the "Scan Tab" on the application's start screen and launch a comprehensive "Full Scan" to examine your entire computer. This inclusive scan encompasses the memory, startup items, the registry, services, drivers, and all files, ensuring that it detects malware hidden in all possible locations.

Scan for Cdxx Virus Ransomware

Be patient, as the scan duration depends on the number of files and your computer's hardware capabilities. Use this time to relax or attend to other tasks.

5. Upon completion, Anti-Malware will present a detailed report containing all the detected malicious items and threats on your PC.

The Cdxx Virus was Found

6. Select all the identified items from the report and confidently click the "Clean Now" button. This action will safely remove the malicious files from your computer, transferring them to the secure quarantine zone of the anti-malware program to prevent any further harmful actions.

The Cdxx Virus has been removed

8. If prompted, restart your computer to finalize the full system scan procedure. This step is crucial to ensure thorough removal of any remaining threats. After the restart, Gridinsoft Anti-Malware will open and display a message confirming the completion of the scan.

Remember Gridinsoft offers a 6-day free trial. This means you can take advantage of the trial period at no cost to experience the full benefits of the software and prevent any future malware infections on your system. Embrace this opportunity to fortify your computer's security without any financial commitment.

Trojan Killer for “Cdxx Virus” removal on locked PC

In situations where it becomes impossible to download antivirus applications directly onto the infected computer due to malware blocking access to websites, an alternative solution is to utilize the Trojan Killer application.

Trojan Killer - Main View

There is a really little number of security tools that are able to be set up on the USB drives, and antiviruses that can do so in most cases require to obtain quite an expensive license. For this instance, I can recommend you to use another solution of GridinSoft - Trojan Killer Portable. It has a 14-days cost-free trial mode that offers the entire features of the paid version. This term will definitely be 100% enough to wipe malware out.

Trojan Killer is a valuable tool in your cybersecurity arsenal, helping you to effectively remove malware from infected computers. Now, we will walk you through the process of using Trojan Killer from a USB flash drive to scan and remove malware on an infected PC. Remember, always obtain permission to scan and remove malware from a computer that you do not own.

Step 1: Download & Install Trojan Killer on a Clean Computer:

1. Go to the official GridinSoft website (gridinsoft.com) and download Trojan Killer to a computer that is not infected.

Download Trojan Killer

2. Insert a USB flash drive into this computer.

3. Install Trojan Killer to the "removable drive" following the on-screen instructions.

Install Trojan Killer to Removable Drive

4. Once the installation is complete, launch Trojan Killer.

Step 2: Update Signature Databases:

5. After launching Trojan Killer, ensure that your computer is connected to the Internet.

6. Click "Update" icon to download the latest signature databases, which will ensure the tool can detect the most recent threats.

Click Update Button

Step 3: Scan the Infected PC:

7. Safely eject the USB flash drive from the clean computer.

8. Boot the infected computer to the Safe Mode.

9. Insert the USB flash drive.

10. Run tk.exe

11. Once the program is open, click on "Full Scan" to begin the malware scanning process.

Searching Cdxx Virus Virus

Step 4: Remove Found Threats:

12. After the scan is complete, Trojan Killer will display a list of detected threats.

Searching Cdxx Virus Finished

13. Click on "Cure PC!" to remove the identified malware from the infected PC.

14. Follow any additional on-screen prompts to complete the removal process.

Restart needed

Step 5: Restart Your Computer:

15. Once the threats are removed, click on "Restart PC" to reboot your computer.

16. Remove the USB flash drive from the infected computer.

Congratulations on effectively removing Cdxx Virus and the concealed threats from your computer! You can now have peace of mind, knowing that they won't resurface again. Thanks to Gridinsoft's capabilities and commitment to cybersecurity, your system is now protected.

Video Guide


How To Decrypt .cdxx Files?

How to restore big files?

Try removing .cdxx extension on a few big files and opening them. This malware has issues with large file encryption. Either the virus scanned and did not lock the file, or it failed and did not add the filemarker. If your files are very large (2GB+), the latter is most likely. Please, let me know in the comments if that will work for you.

The newest extensions were released around the end of August 2019 after the criminals made changes. This includes Cdtt, Cdpo, Cdwe etc.

As an outcome of the changes made by the criminals, STOPDecrypter is no longer supported. It has been replaced with the Emsisoft Decryptor for STOP Djvu Ransomware developed by Emsisoft.

You can download free decryption tool here: Decryptor for STOP Djvu.

  1. Download and run the decryption tool.

    Start downloading the decryption tool.

    Make sure to launch the decryption utility as an administrator. You need to agree with the license terms that will come up. For this purpose, click on the “Yes” button:

    Emsisoft Decryptor - license terms

    As soon as you accept the license terms, the main decryptor user interface comes up:

    Emsisoft Decryptor - user interface

  2. Select folders for decryption.

    Based on the default configurations, the decryptor will by default choose the accessible directories to decrypt the currently reachable drives (the connected ones), including the network drives. Additional (optional) locations can be selected with the aid of the “Add” button.

    Decryptors usually propose several options depending on the specific malware family. The present possible options are displayed in the Options tab and can be enabled or turned off there. You may locate a comprehensive list of the currently active Options below.

  3. Click on the “Decrypt” button.

    As soon as you add all the desired locations for decryption to the list, click on the “Decrypt” button to initiate the decryption procedure.

    Note that the main screen may turn you to a status view, letting you know of the active process and the decryption statistics of your data:

    Emsisoft Decryptor - the decryption statistics

    The decryptor will notify you once the decryption procedure is completed. If you need the report for your papers, you can save it by choosing the “Save log” button. Note that it is also possible to copy it directly to your clipboard and paste it into emails or messages here if you need to do so.

The Emsisoft Decryptor might display different messages after a failed attempt to restore your files:

✓ Error: Unable to decrypt file with ID: [your ID]

Emsisoft failed to find a corresponding decryption key in their database.

✓ No key for New Variant online ID: [your ID]

Notice: this ID appears to be an online ID, decryption is impossible

Malware uses an online key to cipher your files. There is no one to share the decryption key with you. Recovery of files without paying the criminals is impossible. 🙁

✓ Result: No key for new variant offline ID: [example ID]

This ID appears to be an offline ID. Decryption may be possible in the future.

Malware used an offline key, but files could not be restored (the offline decryption key isn’t available yet). But, this message is good news for you, since it is possible to restore your files in the future. 🙂

It can take a few weeks or months until the decryption key gets found and uploaded to the decryptor. Please follow updates regarding the decryptable DJVU versions here.

✓ Remote name could not be resolved

This stands for a DNS issue present in your system. Consider resetting your HOSTS file to default.

How to Restore .cdxx Files?

In some cases ransomware is not doom for your files…

The Cdxx ransomware encryption mechanism is next: it ciphers every file byte-by-byte, then saves a file copy, deleting (not overriding!) the original file. Thus, the data of the file location on the disk drive is lost, but the original file is not removed from the physical disk. The cell, or the sector where this file was stored, can still keep this file, but it is not present in the file system and can be overwritten by data that has been loaded to this disk after the removal. Hence, it is possible to recover your files using special software.

I recently had my PC infected by this virus. It managed to bypass 2 Antivirus software and 2 malware fighters.

Anyway, after realizing it was an online algorithm, it was impossible to retrieve my encrypted files. I also had my backup drive plugged in at the time of the virus, and this was also infected, or so I thought. Every folder within my backup drive had been infected and was encrypted. However, despite losing some important files, I retrieved almost 80% of my 2TB storage.

When I started going through the folders, I noticed the readme.txt ransom note in every folder. I opened some of the folders and found that all files that were not in a subfolder within that folder had been encrypted. However, I found a flaw and a glimmer of hope when I went into the subfolders in other folders and found that these files had not been encrypted. Every folder within my c and d drives, including subfolders, had been encrypted, but this was not the case with the backup drive. Having subfolders created within a folder has saved 80% of my data.

As I said, I believe this to be only a small loophole on a backup drive. I’ve since found a further 10 % of my data on another hard drive on a different PC. So my advice is if you use a backup drive, create subfolders. I was lucky, I guess. But I was also unlucky that the virus hit as I was transferring some files from my backup.

Hopefully, this can help some other people in my situation.

Jamie Newland
Some pointers for recovery repair of Cdxx files (true for all STOP/DJVU variants):

  • I have seen Stop/Djvu variants fail to encrypt deeper nested folders, so that you can check that. You may find those are not encrypted.
  • This ransomware saves encrypted data to a new file and deletes the original. So there’s a slight chance part of that deleted file can be recovered using file recovery software. It’s unlikely the folder structure can be restored, so a free tool like PhotoRec may be as good as any.
  • This ransomware only partially encrypts (about the first 150 KB), so depending on file size and type of data, the non-encrypted part may be recoverable.
  • Joep

    Recovering your files with PhotoRec

    PhotoRec is a free open-source program, which is initially created for data recovery from damaged disks, or data recovery in case they are unintentionally deleted. However, with time flow, this program adopted the ability to restore the files of 400 different file types. Hence, it can be used for data recovery after the Cdxx attack.

    First, you need to download this app. It is 100% free, but the developer notifies you that there is no guarantee that your files will be retrieved. PhotoRec is distributed together with another utility of the same developer – TestDisk. The program archive will bear the TestDisk name but don’t worry. PhotoRec files are right inside.

    To run PhotoRec, find and open “qphotorec_win.exe” file. No installation is required – this program has all the files it needs within the archive, hence, you can mount it on your USB drive, and help your friends/parents/anyone who has been attacked by Cdxx ransomware.

    PhotoRec file in the folder for restore Cdxx files

    Upon the start, you will encounter the screen showing you the complete list of your disk drives. However, this information is probably irrelevant, because the required menu is placed a bit higher. Click this menu, then choose the disk which was attacked by ransomware.

    Choose the disc in PhotoRec

    After picking the disk, you need to pick the destination folder for the retrieved files. This menu is located at the lower part of the PhotoRec window. The best choice is to export them on a USB drive or any other type of removable disk.

    Choosing the destination folder of recovery Cdxx files

    Then, you need to indicate the file formats. This setting is located at the bottom, too. As it was mentioned, PhotoRec can regain the files in about 400 different formats.

    Choose the file format

    Finally, you can initiate file recovery by pressing the “Search” button. You will see the screen where the outcomes of the scan and recovery are shown.

    Recovery process

    Cdxx files recovery Video Guide.


    Frequently Asked Questions

    🤔 How can I open “.cdxx” files?

    No way. These files are encrypted by ransomware. The contents of encrypted files are not available until they are decrypted.

    🤔 This virus has blocked the infected PC: I can’t get the activation code.

    In this situation, you need to prepare the memory stick with a pre-installed Trojan Killer.

    🤔 Decryptor did not decrypt all my files, or not all of them were decrypted. What should I do?

    Have patience. You are infected with the new version of STOP/DJVU ransomware, and decryption keys have not yet been released. Follow the news on our website.

    We will keep you posted when new keys or new decryption programs appear.

    🤔 What can I do right now?

    The Cdxx ransomware encrypts only the first 150KB of files. So MP3 files are rather large, some media players (Winamp for example) may be able to play the files, but – the first 3-5 seconds (the encrypted portion) will be missing.

    You can try to find a copy of an original file that was encrypted:

    • Files you downloaded from the Internet that were encrypted and you can download again to get the original.
    • Pictures that you shared with family and friends that they can just send back to you.
    • Photos that you uploaded on social media or cloud services like Carbonite, OneDrive, iDrive, Google Drive, etc
    • Attachments in emails you sent or received and saved.
    • Files on an older computer, flash drive, external drive, camera memory card, or iPhone where you transferred data to the infected computer.

    If the guide doesn’t help you to remove the infection, please download the GridinSoft Anti-Malware that I recommended. Do not forget to share your experience in solving the problem. Please leave a comment here! This can help other victims to understand they are not alone. And together we will find ways to deal with this issue.

    I need your help to share this article.

    It is your turn to help others. I have written this guide to help people like you. You can use the buttons below to share this on your favorite social media Facebook, Twitter, or Reddit.

    Brendan Smith
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    References

    1. My files are encrypted by ransomware, what should I do now?
    2. About DJVU (STOP) Ransomware.
    Summary
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    Software Name
    CDXX Virus
    Operating System
    Windows
    Software Category
    Ransomware
    Price
    USD 999
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    About the author

    Brendan Smith

    I'm Brendan Smith, a passionate journalist, researcher, and web content developer. With a keen interest in computer technology and security, I specialize in delivering high-quality content that educates and empowers readers in navigating the digital landscape.

    With a focus on computer technology and security, I am committed to sharing my knowledge and insights to help individuals and organizations protect themselves in the digital age. My expertise in cybersecurity principles, data privacy, and best practices allows me to provide practical tips and advice that readers can implement to enhance their online security.

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