Kook is a DJVU family of ransomware-type infections1. The ransomware encrypts your private files (video, photos, documents). The encrypted files can be tracked by specific “.kook” extension. So, you can’t open them at all.
In this guide I will try to help you remove Kook virus without any payment. As bonus I will assist you in decoding your encrypted files.
What is “Kook”?
Kook can be correctly identify as a ransomware infection.
Ransomware is a specific kind of virus that encrypted your documents and then forces you to pay for them. DJVU (aka STOP) ransomware family was first revealed and discovered by virus analyst Michael Gillespie2.
Kook is basically similar to other representatives of ransomware like: Erif, Kuus, Bmic. Kook encrypted all common file types. Hence, users cannot use the own documents . Kook adds its own “.kook” extension into all files. For example, the file “video.avi”, will be changed into “video.avi.kook”. As soon as the encryption is accomplished, Kook drops a specific text file “_readme.txt” and puts it into all folders that contain the modified files.
Here is a summary for the Kook ransomware:
|Ransomware family3||DJVU/STOP4 ransomware|
|Ransom||From $490 to $980 (in Bitcoins)|
|Detection5||MSIL/Kryptik.WZZ, Ursu.594782, Razy.511934|
|Symptoms||Your files (photos, videos, documents) have a .kook extension and you can’t open it|
|Fix Tool||See If Your System Has Been Affected by .kook file virus|
This text asking payment is for get files back via decryption key:
The cryptography algorithm used by Kook is AES-256. So, if your files got encrypted with a specific decryption key, which is totally unique and there are no other copies. The sad reality is that it is impossible to recover the information without the unique key available.
In case if Kook worked in online mode, it is impossible for you to gain access to the AES-256 key. It is stored on a distant server owned by the frauds who promote the Kook ransomware.
For receiving decryption key the payment should be $980. To obtain the payment details, the victims are encouraged by the message to contact the frauds by email (email@example.com), or via Telegram.
Do not pay for Kook!
Please, try to use the available backups, or Decrypter tool
_readme.txt file also indicates that the computer owners must get in touch with the Kook representatives during 72 hours starting from the moment of files where encrypted. On the condition of getting in touch within 72 hours, users will be granted a 50% rebate. Thus the ransom amount will be minimized down to $490). However, stay away from paying the ransom!
I strongly advise that you do not contact these frauds and do not pay. The one of the most real working solution to recover the lost data – just using the available backups, or use Decrypter tool.
The peculiarity of all such viruses apply a similar set of actions for generating the unique decryption key to recover the ciphered data.
Thus, unless the ransomware is still under the stage of development or possesses with some hard-to-track flaws, manually recovering the ciphered data is a thing you can’t perform. The only solution to prevent the loss of your valuable data is to regularly make backups of your crucial files.
Note that even if you do maintain such backups regularly, they ought to be put into a specific location without loitering, not being connected to your main workstation.
For instance, the backup may be kept on the USB flash drive or some alternative external hard drive storage. Optionally, you may refer to the help of online (cloud) information storage.
Needless to mention, when you maintain your backup data on your common device, it may be similarly ciphered as well as other data.
For this reason, locating the backup on your main PC is surely not a wise idea.
How I was infected?
Kook has a various methods to built into your system. But it doesn’t really matter what way was used in your case.
Kook ransomware attack following a successful phishing attempt.
Nevertheless, these are the common leaks through which it may be injected into your PC:
- hidden installation along with other apps, especially the utilities that work as freeware or shareware;
- dubious link in spam emails leading to the Kook installer
- online free hosting resources;
- using illegal peer-to-peer (P2P) resources for downloading pirated software.
There were cases when the Kook virus was disguised as some legitimate tool, for example, in the messages demanding to initiate some unwanted software or browser updates. This is typically the way how some online frauds aim to force you into installing the Kook ransomware manually, by actually making you directly participate in this process.
Surely, the bogus update alert will not indicate that you are going to actually inject the Kook ransomware. This installation will be concealed under some alert mentioning that allegedly you should update Adobe Flash Player or some other dubious program whatsoever.
Of course, the cracked apps represent the damage too. Using P2P is both illegal and may result in the injection of serious malware, including the Kook ransomware.
To sum up, what can you do to avoid the injection of the Kook ransomware into your device? Even though there is no 100% guarantee to prevent your PC from getting damaged, there are certain tips I want to give you to prevent the Kook penetration. You must be cautious while installing free software today.
Make sure you always read what the installers offer in addition to the main free program. Stay away from opening dubious email attachments. Do not open files from the unknown addressees. Of course, your current security program must always be updated.
The malware does not speak openly about itself. It will not be mentioned in the list of your available programs. However, it will be masked under some malicious process running regularly in the background, starting from the moment when you launch your PC.
The message by the Kook ransomware states the following frustrating information:
ATTENTION! Don't worry, you can return all your files! All your files like photos, 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-WJa63R98Ku 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: firstname.lastname@example.org Reserve e-mail address to contact us: email@example.com Your personal ID: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
The image below gives a clear vision of how the files with “.kook” extension look like:
How to remove Kook virus?
In addition to encode a victim’s files, the Kook virus has also started to install the Azorult Spyware on computer to steal account credentials, cryptocurrency wallets, desktop files, and more.
Reasons why I would recommend GridinSoft6
There is no better way to recognize, remove and prevent ransomware than to use an anti-malware software from GridinSoft7.
Download Removal Tool.
You can download GridinSoft Anti-Malware by clicking the button below:
Run the setup file.
When setup file has finished downloading, double-click on the setup-antimalware-fix.exe file to install GridinSoft Anti-Malware on your computer.
An User Account Control asking you about to allow GridinSoft Anti-Malware to make changes to your device. So, you should click “Yes” to continue with the installation.
Press “Install” button.
Once installed, Anti-Malware will automatically run.
Wait for the Anti-Malware scan to complete.
GridinSoft Anti-Malware will automatically start scanning your computer for Kook infections and other malicious programs. This process can take a 20-30 minutes, so I suggest you periodically check on the status of the scan process.
Click on “Clean Now”.
When the scan has finished, you will see the list of infections that GridinSoft Anti-Malware has detected. To remove them click on the “Clean Now” button in right corner.
How to decrypt .kook files?
Restore solution for big “.kook files“
Try removing .kook extension on a few BIG files and opening them. Either the Kook infection read and did not encrypt the file, or it bugged and did not add the filemarker. If your files are very large (2GB+), the latter is most likely. Please, let me know in comments if that will work for you.
As a result of the changes made by the criminals, STOPDecrypter is no longer supported. It has been removed and replaced with the Emsisoft Decryptor for STOP Djvu Ransomware developed by Emsisoft and Michael Gillespie.
You can download free decryption tool here: Decryptor for STOP Djvu.
Download and run 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:
As soon as you accept the license terms, the main decryptor user interface comes up:
Select folders for decryption.
Based on the default settings, the decryptor will automatically populate the available locations in order to decrypt the currently available drives (the connected ones), including the network drives. Extra (optional) locations can be selected with the help of the “Add” button.
Decryptors normally suggest several options considering the specific malware family. The current possible options are presented in the Options tab and can be activated or deactivated there. You may locate a detailed list of the currently active Options below.
Click on the “Decrypt” button.
As soon as yo add all the desired locations for decryption into the list, click on the “Decrypt” button in order 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:
The decryptor will notify you as soon as the decryption procedure is completed. If you need the report for your personal 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 to paste it into emails or forum messages if you need to do so.
Frequently Asked Questions
📂 How can I open “.kook” files?
No way. These files are encrypted by Kook ransomware. The contents of .kook files are not available until they are decrypted.
⏰ Kook files contain important information. How can I decrypt them urgently?
If your data remained in the .kook files are very valuable, then most likely you made a backup copy.
If not, then you can try to restore them through the system function – Restore Point.
All other methods will require patience.
📑 You have advised using GridinSoft Anti-Malware to remove Kook. Does this mean that the program will delete my encrypted files?
Of course not. Your encrypted files do not pose a threat to the computer. What happened has already happened.
You need GridinSoft Anti-Malware to remove active system infections. The virus that encrypted your files is most likely still active and periodically runs a test for the ability to encrypt even more files. Also, these viruses install keyloggers and backdoors for further malicious actions (for example, theft of passwords, credit cards) often.
🔐 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 Kook ransomware, and decryption keys have not yet been released. Follow the news on our website.
We will keep you posted on when new Kook keys or new decryption programs appear.
❓ What can I do right now?
The Kook 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.
Also,You can contact the following government fraud and scam sites to report this attack:
- In the United States: On Guard Online;
- In Canada: Canadian Anti-Fraud Centre;
- In the United Kingdom: Action Fraud;
- In Australia: SCAMwatch;
- In New Zealand: Consumer Affairs Scams;
- In France: Agence nationale de la sécurité des systèmes d’information;
- In Germany: Bundesamt für Sicherheit in der Informationstechnik;
- In Ireland: An Garda Síochána;
It’s my favorite video tutorial: How to use GridinSoft Anti-Malware and Emsisoft Decryptor for fix ransomware infections.
If the guide doesn’t help you to remove Kook infection, please download the GridinSoft Anti-Malware that I recommended. Also, you can always ask me in the comments for getting help. Good luck!
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KOOK Virus Removal
Name: KOOK Virus
Description: KOOK Virus is a DJVU family of ransomware-type infections. This infection encrypts important personal files (video, photos, documents). The encrypted files can be tracked by a specific .kook extension. So, you can't use them at all.
Operating System: Windows
User Review( votes)
- Ransomware-type infection: https://en.wikipedia.org/wiki/Ransomware
- Twitter: https://twitter.com/demonslay335
- My files are encrypted by ransomware, what should I do now?
- About DJVU (STOP) Ransomware.
- Encyclopedia of threats.
- GridinSoft Anti-Malware Review from HowToFix site: https://howtofix.guide/gridinsoft-anti-malware/
- More information about GridinSoft products: https://gridinsoft.com/products/