Kook ransomware removal instructions
What is Kook?
Kook is a piece of malicious software, belonging to the Djvu rasomware family. Systems infected with this malware have their data encrypted and they receive ransom demands for the decryption tools/software. During the encryption process, all of the compromised files are appended with the ".kook" extension. For example, a file named something like "1.jpg would appear as "1.jpg.kook" - following encryption. Once this process is complete, a ransom note - "_readme.txt" - is created.
The ransom-demanding message in "_readme.txt" states that all of the victims' files have been encrypted. To restore the data, users are instructed to purchase decryption tools/keys from the cyber criminals behind the Kook infection. The price of the recovery tools is stated to be 980 USD; should contact with the criminals be established (via email) within the first 72 hours - the ransom can be halved (490 USD). Before making the payment, victims can test decryption by sending the criminals one encrypted file, containing no valuable information. If after initiating communication, no response arrives in 6 hours - users are to check their "Junk/Spam" email folders for the reply. Unfortunately, in most cases of ransomware attacks, without interference of the cyber criminals responsible - decryption is impossible. It might be, if the malicious software is still in development and/or has significant flaws. Whatever the case, it is strongly advised against meeting the ransom demands. Since often, despite paying - victims do not receive the promised decryption tools/software. Hence, their data remains encrypted and they experience financial loss. To prevent Kook ransomware from further encryptions, it must be eliminated from the operating system. However, removal will not restore already affected files. The sole solution is recovering them from a backup, if one was created prior to the infection and was stored in a different location.
Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:
[Zfile@Tuta.Io], FlyingShip and Zbw are a couple examples of other ransomware-type programs. They are designed to encrypt data and demand payment for the decryption. There are two key differences between these programs/infections - the cryptographic algorithms they use (symmetric or asymmetric) and size of the demanded sum. Ransoms tend to range from three to four digits in USD. Cyber criminals typically demand the payments to be made in digital currencies (e.g. cryptocurrencies, pre-paid vouchers, etc.), due to transactions of them being difficult/impossible to trace. To ensure data safety, it is highly recommended to keep backups in unplugged storage devices and/or remote servers (preferably, in multiple separate locations).
How did ransomware infect my computer?
|Threat Type||Ransomware, Crypto Virus, Files locker|
|Detection Names||Avast (FileRepMetagen [Malware]), ESET-NOD32 (A Variant Of Win32/GenKryptik.EPJX), Kaspersky (Trojan.Win32.Chapak.esiy), Malwarebytes (Trojan.MalPack.GS), Full List Of Detections (VirusTotal)|
|Encrypted Files Extension||.kook|
|Ransom Demanding Message||_readme.txt|
|Cyber Criminal Contactfirstname.lastname@example.org and email@example.com|
|Symptoms||Cannot open files stored on your computer, previously functional files now have a different extension (for example, my.docx.locked). A ransom demand message is displayed on your desktop. Cyber criminals demand payment of a ransom (usually in bitcoins) to unlock your files.|
|Additional Information||This malware is designed to show a fake Windows Update window and modify the Windows "hosts" file to prevent users from accessing cyber security websites (more information below). This ransomware is also designed to disable the Windows Task Manager.|
|Distribution methods||Infected email attachments (macros), torrent websites, malicious ads, unofficial activation and updating tools.|
|Damage||All files are encrypted and cannot be opened without paying a ransom. Additional password-stealing trojans and malware infections can be installed together with a ransomware infection.|
|Malware Removal (Windows)||
To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Malwarebytes.
How to protect yourself from ransomware infections?
Suspicious and/or irrelevant emails must not be opened, especially any attachments and/or links present in them - as doing so can result in a system infection. Only official and verified download channels must be used. Additionally, all programs must be activated/updated with tools or functions provided by legitimate developers. Illegal activation ("cracking") tools and third party updaters are advised against use, as they are commonly used to proliferate malware. To protect device and user safety, it is crucial to have a dependable anti-virus/anti-spyware suite installed. Furthermore, this software must be kept updated, used to perform regular system scans and to remove detected/potential threats. If your computer is already infected with Kook, we recommend running a scan with Malwarebytes for Windows to automatically eliminate this ransomware.
Text presented in Kook ransomware's text file ("_readme.txt"):
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:
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:
Your personal ID:
Screenshot of files encrypted by Kook (".kook" extension):
Screenshot of a pop-up displayed when trying to open the Task Manager after executing Kook ransomware:
Screenshot of fake Windows update pop-up displayed during the encryption:
IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also add a number of entries to the Windows "hosts" file. The entries contain URLs of various websites, most of which are related to malware removal. This is done to prevent users from accessing malware security websites and seeking help. Our website (PCrisk.com) is also on the list. Removing these entries, however, is simple - you can find detailed instructions in this article (note that, although the steps are shown in the Windows 10 environment, the process is virtually identical on all versions of the Microsoft Windows operating system).
Screenshot of websites added to Windows hosts file:
There are currently two versions of Djvu ransomware infections: old and new. The old versions were designed to encrypt data by using a hard-coded "offline key" whenever the infected machine had no internet connection or the server was timing out/not responding. Therefore, some victims were able to decrypt data using a tool developed by cyber security researcher, Michael Gillespie, however, since the encryption mechanism has been slightly changed (hence the new version, released in August, 2019), the decrypter no longer works and it is not supported anymore. If your data has been encrypted by an older version, you might be able to restore it with the another tool developed by Emsisoft and Michael Gillespie. It supports a total of 148 Djvu's variants and you can find more information, as well as download link and decryption instructions in Emsisoft's official page.
Screenshot of Djvu decryption tool by Emsisoft and Michael Gillespie:
Additionally, Emsisoft is now providing a service that allows to decrypt data (again, only if it was encrypted by Djvu variants released before August, 2019) for those victims who have a pair of the same file before and after the encryption. All victims have to do is upload a pair of original and encrypted file to Emsisoft's Djvu decryption page and download the aforementioned decryption tool (the download link will be provided after uploading files). Note that the file processing may take some time so be patient. It is also worth mentioning that the system must have an Internet connection during the entire decryption process, otherwise it will fail.
Screenshot of Emsisoft's Djvu decryption service page:
Kook ransomware removal:
Instant automatic malware removal:
Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Malwarebytes is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
- What is Kook virus?
- STEP 1. Isolating the infected device.
- STEP 2. Identifying the ransomware infection.
- STEP 3. Searching for ransomware decryption tools.
- STEP 4. Restoring files with data recovery tools.
- STEP 5. Creating data backups.
Isolating the infected device:
Some ransomware-type infections are designed to encrypt files within external storage devices, infect them, and even spread throughout the entire local network. For this reason, it is very important to isolate the infected device (computer) as soon as possible.
Step 1: Disconnect from the internet.
The easiest way to disconnect a computer from the internet is to unplug the Ethernet cable from the motherboard, however, some devices are connected via a wireless network and for some users (especially those who are not particularly tech-savvy), disconnecting cables may seem troublesome. Therefore, you can also disconnect the system manually via Control Panel:
- Navigate to the "Control Panel", click the search bar in the upper-right corner of the screen, enter "Network and Sharing Center" and select search result:
- Click the "Change adapter settings" option in the upper-left corner of the window:
- Right-click on each connection point and select "Disable". Once disabled, the system will no longer be connected to the internet. To re-enable the connection points, simply right-click again and select "Enable".
Step 2: Unplug all storage devices.
As mentioned above, ransomware might encrypt data and infiltrate all storage devices that are connected to the computer. For this reason, all external storage devices (flash drives, portable hard drives, etc.) should be disconnected immediately, however, we strongly advise you to eject each device before disconnecting to prevent data corruption:
- Navigate to "My Computer", right-click on each connected device and select "Eject":
Step 3: Log-out of cloud storage accounts.
Some ransomware-type might be able to hijack software that handles data stored within "the Cloud". Therefore, the data could be corrupted/encrypted. For this reason, you should log-out of all cloud storage accounts within browsers and other related software. You should also consider temporarily uninstalling the cloud-management software until the infection is completely removed.
Identify the ransomware infection:
To properly handle an infection, one must first identify it. Some ransomware infections use ransom-demand messages as an introduction (see the WALDO ransomware text file below).
This, however, is rare. In most cases, ransomware infections deliver more direct messages simply stating that data is encrypted and that victims must pay some sort of ransom. Note that ransomware-type infections typically generate messages with different file names (for example, "_readme.txt", "READ-ME.txt", "DECRYPTION_INSTRUCTIONS.txt", "DECRYPT_FILES.html", etc.). Therefore, using the name of a ransom message may seem like a good way to identify the infection. The problem is that most of these names are generic and some infections use the same names, even though the delivered messages are different and the infections themselves are unrelated. Therefore, using the message filename alone can be ineffective and even lead to permanent data loss (for example, by attempting to decrypt data using tools designed for different ransomware infections, users are likely to end up permanently damaging files and decryption will no longer be possible even with the correct tool).
Another way to identify a ransomware infection is to check the file extension, which is appended to each encrypted file. Ransomware infections are often named by the extensions they append (see files encrypted by Qewe ransomware below).
This method is only effective, however, when the appended extension is unique - many ransomware infections append a generic extension (for example, ".encrypted", ".enc", ".crypted", ".locked", etc.). In these cases, identifying ransomware by its appended extension becomes impossible.
One of the easiest and quickest ways to identify a ransomware infection is to use the ID Ransomware website. This service supports most existing ransomware infections. Victims simply upload a ransom message and/or one encrypted file (we advise you to upload both if possible).
The ransomware will be identified within seconds and you will be provided with various details, such as the name of the malware family to which the infection belongs, whether it is decryptable, and so on.
Example 1 (Qewe [Stop/Djvu] ransomware):
Example 2 (.iso [Phobos] ransomware):
If your data happens to be encrypted by a ransomware that is not supported by ID Ransomware, you can always try searching the internet by using certain keywords (for example, ransom message title, file extension, provided contact emails, cryptowallet addresses, etc.).
Search for ransomware decryption tools:
Encryption algorithms used by most ransomware-type infections are extremely sophisticated and, if the encryption is performed properly, only the developer is capable of restoring data. This is because decryption requires a specific key, which is generated during the encryption. Restoring data without the key is impossible. In most cases, cyber criminals store keys on a remote server, rather than using the infected machine as a host. Dharma (CrySis), Phobos, and other families of high-end ransomware infections are virtually flawless, and thus restoring data encrypted without the developers' involvement is simply impossible. Despite this, there are dozens of ransomware-type infections that are poorly developed and contain a number of flaws (for example, the use of identical encryption/decryption keys for each victim, keys stored locally, etc.). Therefore, always check for available decryption tools for any ransomware that infiltrates your computer.
Finding the correct decryption tool on the internet can be very frustrating. For this reason, we recommend that you use the No More Ransom Project and this is where identifying the ransomware infection is useful. The No More Ransom Project website contains a "Decryption Tools" section with a search bar. Enter the name of the identified ransomware, and all available decryptors (if there are any) will be listed.
Restore files with data recovery tools:
Depending on the situation (quality of ransomware infection, type of encryption algorithm used, etc.), restoring data with certain third-party tools might be possible. Therefore, we advise you to use EaseUS Data Recovery Wizard Pro. This tool supports over a thousand data types (graphics, video, audio, documents, etc.) and it is very intuitive (little knowledge is necessary to recover data).
Step 1: Perform a scan.
- Hover your mouse over the partition you wish to scan and select "Scan". You can also select a specific folder, or click shortcut icons to scan the Desktop or Recycle Bin:
- Wait for EaseUS Data Recovery Wizard Pro to complete the scan. The scanning duration depends on the volume of files (both in quantity and size) that you are scanning (for example, several hundreds gigabytes could take over an hour to scan). Therefore, be patient during the scanning process. We also advise against modifying or deleting existing files, since this might interfere with the scan. If you add additional data (for example, downloading files/content) while scanning, this will prolong the process:
Step 2: Recover data.
- Once the process is complete, select the folders/files you wish to restore and simply click "Recover". Note that some free space on your storage drive is necessary to restore data. Note also that the trial version of EaseUS Data Recovery Wizard Pro is only capable of scanning drives and listing recoverable files - to restore them, you must purchase a license:
Step 3: Save the scan session (optional).
- We recommend that you save the scanning session once you have completed recovery, in case you decide to recover additional files later. Simply click the "Save Scan Session" icon in the upper-right corner of the screen and choose the location for the file to be saved. This will save a lot of time, since you will not need to re-scan the storage drive the next time you wish to restore something. Bear in mind, however, that data removed after the scanning session has finished will not be listed:
Create data backups:
Proper file management and creating backups is essential for data security. Therefore, always be very careful and think ahead.
Partition management: We recommend that you store your data in multiple partitions and avoid storing important files within the partition that contains the entire operating system. If you fall into a situation whereby you cannot boot the system and are forced to format the disk on which the operating system is installed (in most cases, this is where malware infections hide), you will lose all data stored within that drive. This is the advantage of having multiple partitions: if you have the entire storage device assigned to a single partition, you will be forced to delete everything, however, creating multiple partitions and allocating the data properly allows you to prevent such problems. You can easily format a single partition without affecting the others - therefore, one will be cleaned and the others will remain untouched, and your data will be saved. Managing partitions is quite simple and you can find all necessary information on Microsoft's documentation web page.
Data backups: The most reliable backup method is to use an external storage device and keep it unplugged. Copy your data to an external hard drive, flash (thumb) drive, SSD, HDD, or any other storage device, unplug it and store it in a dry place away from sun and extreme temperatures. This method is, however, quite inefficient, since data backups and updates need to be made regularly. You can also use a cloud service or remote server. Here, an internet connection is required and there is always the chance of a security breach. Therefore, you should consider using an application to create data backups locally.
We recommend using the EaseUS Todo Backup application. The "Home" edition of EaseUS Todo Backup is usually more than adequate for regular users, however, the "Business" edition is more suitable for companies and large computer networks. The EaseUS Todo Backup application provides extensive data protection features. You can easily create backups, and encrypt and compress them for enhanced protection and storage saving purposes. It also allows you to set backup schedules, create bootable devices, and restore the system if a crash occurs. You can easily choose where to store the created backup: locally; uploaded to an external drive; FTP; cloud storage, or elsewhere. In summary, EaseUS Todo Backup is an all-in-one tool, which provides all features required to properly backup your data.
Creating a data backup:
The backup process is virtually identical regardless of the item (file, partition, entire system) you wish to backup. Taking the File Backup feature as an example:
Step 1: Choose which item to backup.
- Click on the "Menu" icon in the upper-left corner of the screen to reveal the menu and select "File Backup":
- Select the files you want to backup. You can also enter a name and description of the backup that will be created:
Step 2: Change the default settings.
The EaseUS Todo Backup application provides a variety of additional options that can be added/modified while creating the backup. For example, you can encrypt data (add a password), select the compression rate (how much the backup should be compressed), performance (how many system resources should be allocated), add an email notification (you receive an email once the process is complete) and so on.
- To open the options window, click the "Backup options" button in the lower-left corner of the screen:
- Select the settings you want to change and click "Save". You can also reset your changes by clicking "Reset to initial settings":
Step 3: Select the backup destination.
As mentioned above, EaseUS Todo Backup allows you to choose where backups are saved - locally or externally.
- Click the "Browse..." button and select the location you want the backup to be saved:
Step 4: Safety measures and process completion.
Depending on the location you have chosen, there are a number of measures you should or should not take. If you are uploading to an internet-connected location (for example, Cloud storage, FTP, etc.), be sure to maintain your internet connection, otherwise you will have to start again. The same applies to external storage devices - do not unplug them until the process is complete.
- The progress bar displays estimated time remaining until completion. Large backups (hundreds of gigabytes) can take hours to create (depending on storage device speed, internet connection, etc.). Therefore, the application also allows you to optionally choose what the system should do (shut down, sleep or hibernate) once the process has finished:
The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups.