According to the criminals and authors behind KOOK ransomware, the file decryption software costs $490 within 72 hours and $980 later. This ransomware version was first spotted by a researcher M.Gillespie on July 27th and is currently very active as shown by ID-Ransomware website. KOOK file virus is essentially similar to STOP/DJVU versions released previously (ERIF, KUUS, ZIPE, REPL). The main ransomware executable is called [4 random chars].tmp.exe, for example, ry4j.tmp.exe, BED5.tmp.exe, D4ED.tmp.exe, f01e.tmp.exe, d7df.tmp.exe or similar, but it operates with a help of winupdate.exe, a process that impersonates a Windows update to make the victim think that it is the real reason behind unexpected system slowdown. However, the real reason is the data encryption procedure. Once KOOK ransomware locks all files, it modifies Windows HOSTS files by adding a list of websites that share computer security related content. This way, the victim can’t access them when searching for information about the virus online. Finally, it installs a password-stealing Trojan called AZORULT on the system, and saves the host computer’s personal ID to C:/SystemID/PersonalID.txt.

The ransom note, _readme.txt, demands money

KOOK virus is designed to extort victims by turning their personal or work files hostage, so it states the criminals’ offer in the so-called ransom note (_readme.txt file). It says that files were encrypted with extremely strong encryption algorithm, and the only way of restoring (decrypting) them is by purchasing a decryption tool and key from them. It goes without saying that it is a pure form of extortion as the cybercriminals are simply demanding a ransom from the victim. If the victim won’t pay, one will never be able to open his/hers files. The criminals suggest contacting them via provided emails – helpmanager@mail.ch or restoremanager@airmail.cc. After contacting them, the victim receives further instructions how and where to purchase cryptocurrency (such as Bitcoins) and how to transfer it to the criminals. Usually, the attackers provide their virtual cryptocurrency wallet so that the victim could transfer the funds to them. Paying the ransom to the cybercriminals is never a recommended options. That is why we recommend you to ignore it, at least until you read all the possible solutions for your situation. Before taking any further actions, we recommend you to cleanse your computer system from malicious components first. We recommend using RESTORO, which is known to be effective when it comes to virus damage repair.

Virus Details

The ransomware attack on a folder containing personal files is shown below.

Can you decrypt files for free?

The answer whether you can expect to decrypt .kook extension files for free depends on several factors. First, you can restore your files if you have a data backup. Second, you have chances to decrypt your data in the FUTURE, but only if you were affected by offline encryption. Description: KOOK ransomware is a STOP/DJVU virus variant that encrypts victim’s personal files and marks them with additional .kook extension. Following that, the malware drops _readme.txt ransom notes in every affected computer folder. The aim of this virus is to restrict victim’s access to his/hers own files, and force to pay a ransom to the criminals. Offer price: 980 Currency: USD Operating System: Windows Application Category: Ransomware Author: STOP/DJVU authors Therefore, before you start to expect .kook file decryption, you should first check whether you were affected by online or offline encryption version used by the ransomware. Open C:/systemID/PersonalID.txt file created by the virus and check whether at least one of the IDs here end in t1. It is a sign of offline encryption, which means good news for you. If this is the case, follow up the updates in this DJVU decryption guide.

File-encrypting viruses await in illegal downloads

KOOK ransomware victims admit downloading the virus alongside illegal files uploaded online, frequently to peer-to-peer file sharing platforms. Software cracks and tools like KMSPico are used to sneak malware into victims computers unnoticeably. Therefore, if you’re thinking to save money on an official software license, think twice. The ransom amount demanded by the cyber criminals is always higher. In addition, you can download STOP/DJVU and similar ransomware versions from unconfirmed and untrustworthy domains. By visiting suspicious websites stuffed with pop-up or banner ads, you risk accidentally clicking on one of them, and getting redirected to a potentially dangerous website. It is known that adult-oriented and gambling games sites are proved to be of a higher risk and often become hackers’ target, so consider staying away from them. Finally, do not get deceived as dangerous websites might display fake Adobe Flash Player updates for you. These deceptive ads state that victim needs an essential update for the computer and it is vulnerable without it. However, if the victim decides to click on such ad and install the update, one might end up with spyware or malware variant on the computer system. Crypto-malware can be prevented. However, you should read more about common ways to distribute it, and ways to protect yourself and your data against it.

Remove KOOK ransomware and restore personal data

Remove KOOK ransomware virus immediately to cleanse its remains and the malware it installed to your computer. For this matter, we recommend you to follow the instructions given below. After removing the malware, download RESTORO and use it to repair potential virus damage on the system. The recommended software also offers Avira scanning engine to remove malware remains. If you’re considering a manual KOOK ransomware removal scenario, we highly advise against it. Not only crypto-malware are highly complicated viruses, but their components can change from version to version, and finding all of them manually quickly becomes a hardly possible task. Therefore, we suggest you to follow the instructions given below. Do not forget to change all of your passwords after deleting the viruses, and then use your data backups or this KOOK decryption guide afterward. OUR GEEKS RECOMMEND Our team recommends a two-step rescue plan to remove ransomware and other remaining malware from your computer, plus repair caused virus damage to the system: GeeksAdvice.com editors select recommended products based on their effectiveness. We may earn a commission from affiliate links, at no additional cost to you. Learn more. Get INTEGO ANTIVIRUS for Windows to remove ransomware, Trojans, adware and other spyware and malware variants and protect your PC and network drives 24/7. This VB100-certified security software uses state-of-art technology to provide protection against ransomware, Zero-Day attacks and advanced threats, Intego Web Shield blocks dangerous websites, phishing attacks, malicious downloads and installation of potentially unwanted programs. Use INTEGO Antivirus to remove detected threats from your computer. Read full review here. RESTORO provides a free scan that helps to identify hardware, security and stability issues and presents a comprehensive report which can help you to locate and fix detected issues manually. It is a great PC repair software to use after you remove malware with professional antivirus. The full version of software will fix detected issues and repair virus damage caused to your Windows OS files automatically. RESTORO uses AVIRA scanning engine to detect existing spyware and malware. If any are found, the software will eliminate them. Read full review here.

Method 1. Enter Safe Mode with Networking

Before you try to remove KOOK ransomware virus virus, you must start your computer in Safe Mode with Networking. Below, we provide the easiest ways to boot PC in the said mode, but you can find additional ones in this in-depth tutorial on our website – How to Start Windows in Safe Mode. Also, if you prefer a video version of the tutorial, check our guide How to Start Windows in Safe Mode on Youtube. Instructions for Windows XP/Vista/7 users Instructions for Windows 8/8.1/10/11 users Now, you can search for and remove KOOK ransomware virus files. It is very hard to identify files and registry keys that belong to the ransomware virus, Besides, malware creators tend to rename and change them repeatedly. Therefore, the easiest way to uninstall such type of a computer virus is to use a reliable security program such as INTEGO Antivirus. For virus damage repair, consider using RESTORO.

Method 2. Use System Restore

In order to use System Restore, you must have a system restore point, created either manually or automatically. Instructions for Windows XP/Vista/7 users Instructions for Windows 8/8.1/10/11 users After restoring the system, we recommend scanning the system with antivirus or anti-malware software. In most cases, there won’t be any malware remains, but it never hurts to double-check. In addition, we highly recommend checking ransomware prevention guidelines provided by our experts in order to protect your PC against similar viruses in the future.

Alternative software recommendations

Malwarebytes Anti-Malware Removing spyware and malware is one step towards cybersecurity. To protect yourself against ever-evolving threats, we strongly recommend purchasing a Premium version of Malwarebytes Anti-Malware, which provides security based on artificial intelligence and machine learning. Includes ransomware protection. See pricing options and protect yourself now.

System Mechanic Ultimate Defense If you’re looking for an all-in-one system maintenance suite that has 7 core components providing powerful real-time protection, on-demand malware removal, system optimization, data recovery, password manager, online privacy protection and secure driver wiping technology. Therefore, due to its wide-range of capabilities, System Mechanic Ultimate Defense deserves Geek’s Advice approval. Get it now for 50% off. You may also be interested in its full review.

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Decrypt KOOK files

Fix and open large KOOK files easily:

It is reported that STOP/DJVU ransomware versions encrypt only the beginning 150 KB of each file to ensure that the virus manages to affect all files on the system. In some cases, the malicious program might skip some files at all. That said, we recommend testing this method on several big (>1GB) files first.

STOP/DJVU decryption tool usage guide

STOP/DJVU ransomware versions are grouped into old and new variants. KOOK ransomware virus is considered the new STOP/DJVU variant, just like BPTO, ISWR, ISZA, BPSM, ZOUU, MBTF, ZNSM (find full list here). This means full data decryption is now possible only if you have been affected by offline encryption key. To decrypt your files, you will have to download Emsisoft Decryptor for STOP DJVU, a tool created and maintained by a genius security researcher Michael Gillespie. Note! Please do not spam the security researcher with questions whether he can recover your files encrypted with online key - it is not possible. In order to test the tool and see if it can decrypt KOOK files, follow the given tutorial.

Meanings of decryptor’s messages

The KOOK decryption tool might display several different messages after failed attempt to restore your files. You might receive one of the following messages: Error: Unable to decrypt file with ID: [example ID] This message typically means that there is no corresponding decryption key in the decryptor’s database. No key for New Variant online ID: [example ID]Notice: this ID appears to be an online ID, decryption is impossible This message informs that your files were encrypted with online key, meaning no one else has the same encryption/decryption key pair, therefore data recovery 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. If you were informed that an offline key was used, but files could not be restored, it means that the offline decryption key isn’t available yet. However, receiving this message is extremely good news, meaning that it might be possible to restore your KOOK extension files in the future. It can take a few months until the decryption key gets found and uploaded to the decryptor. We recommend you to follow updates regarding the decryptable DJVU versions here. We strongly recommend backing up your encrypted data and waiting.

Victims of KOOK ransomware virus should report the Internet crime incident to the official government fraud and scam website according to their country:

In the United States, go to the On Guard Online website.In Australia, go to the SCAMwatch website.In Germany, go to the Bundesamt für Sicherheit in der Informationstechnik website.In Ireland, go to the An Garda Síochána website.In New Zealand, go to the Consumer Affairs Scams website.In the United Kingdom, go to the Action Fraud website.In Canada, go to the Canadian Anti-Fraud Centre.In India, go to Indian National Cybercrime Reporting Portal.In France, go to the Agence nationale de la sécurité des systèmes d’information.

If you can’t find an authority corresponding to your location on this list, we recommend using any search engine to look up “[your country name] report cyber crime”. This should lead you to the right authority website. We also recommend staying away from third-party crime report services that are often paid. It costs nothing to report Internet crime to official authorities. Another recommendation is to contact your country’s or region’s federal police or communications authority.