Koolova Ransomware

Also Known As: Koolova virus
Distribution: Low
Damage level: Severe

Koolova ransomware removal instructions

What is Koolova?

First discovered by security researcher, Michael Gillespie, Koolova is a high-risk virus (ransomware-type virus) and is also known as Koolova virus. Koolova encrypts files using the AES-256 encryption algorithm, which is a symmetric algorithm. You can read it about it here. All encrypted files are modified and extensions changed from (for example) "1.jpg" to "1.jpg.encrypted".

Koolova's developer is presented as an evil computer virus called Jigsaw, but is more commonly known as Jigsaw's twin who claims that he has encrypted all users' personal files (such as photos, pictures, documents, and so on). Unlike most ransomware developers and cyber criminals, people associated with the Koolova virus do not demand ransom payments in return for users' files. The only requirement is to stop downloading 'unsafe applications' from the internet. It even warns users that if they continue to download unsafe apps, they might encounter more serious problems caused by another virus. According to Jigsaw's twin Koolova developer, instructions on how to decrypt files are given at the bottom of the displayed message. Furthermore, there is a timer, which indicates how much time remains for users to decrypt their files. According to them, if the time elapses, users will lose all encrypted files. It is unknown whether Koolova's developer/s will also demand payment for decryption of files. Even if they do, note that cyber criminals should not be trusted and their demands should be ignored. As a rule, cyber criminals ignore victims even when they have paid ransoms. Therefore, they should not be contacted via email addresses or any other means. In most cases, it is impossible to decrypt files free of charge, and there is no guarantee that Koolova developers will return files regardless of any ransom payment or otherwise. The only possible free solution is to restore everything from a backup.

Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:


Koolova is similar or identical to a number of other ransoware-type viruses such as Gamma, Scarab-Hitler, Rektware, and CryptoConsole. Ransomware-type viruses might be developed by different cyber criminals and thus have different behavior, but most share the same purposes: to encrypt data and make ransom demands. Usually, the only variables are cost of decryption and encryption algorithm/s used. Most of these viruses use algorithms that generate individual/unique decryption keys, so unless the virus is still in a development state or contains unfixed bugs, it is impossible to decrypt files without using a specific decryption key. To prevent further attacks (data loss), we recommend that you maintain data backups regularly and keep them on an unplugged storage device, remote server, or other storage area that cannot be reached by cyber criminals.

How did ransomware infect my computer?

There are a number of different ways that systems become infected with ransomware-type viruses such as Koolova. Some common methods are unofficial software download sources, spam email campaigns, fake software update tools, trojans, and P2P (peer-to-peer) networks. Unofficial software download sources (websites offering to download freeware, free file hosting websites, and so on) and P2P networks (torrents, eMule, and others) often present untrustworthy executables as legitimate applications. Spam campaigns are used to distribute attachments in emails sent from suspicious/unknown users. When these attachments are opened, they download and install malicious software. Fake software updaters often have two ways of infecting computers: exploiting outdated software bugs or other problems, and; downloading malware rather than the promised updates. Trojans cause chain infections (one virus proliferates another). Note that careless behaviour by some users often leads to various computer infections.

Threat Summary:
NameKoolova virus
Threat TypeRansomware, Crypto Virus, Files locker
SymptomsCan't open files stored on your computer, previously functional files now have a different extension, for example my.docx.locked. A ransom demanding message is displayed on your desktop. Cyber criminals are asking to pay a ransom (usually in bitcoins) to unlock your files.
Distribution methodsInfected email attachments (macros), torrent websites, malicious ads.
DamageAll 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.
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How to protect yourself from ransomware infections?

Browse the web and download/install or update software with care. Do not open irrelevant email attachments that are sent from unknown or suspicious senders. Keep your software updated but do this using implemented, official tools that are provided by software developers. Download software using official and trustworthy websites, and direct links. Avoid using third party downloaders, torrents, and peer-to-peer networks. These often download your chosen software together with potentially unwanted applications or even malware. Finally, have a reputable antivirus software installed and keep it enabled at all times. If your computer is already infected with Koolova, we recommend running a scan with Malwarebytes for Windows to automatically eliminate this ransomware.

Text presented in Koolova ransomware message:

Hello, I'm nice Jigsaw or more commonly known as Jigsaws twin.
Unfortunately all of your personal files (pictures, documents, etc...) have been encrypted by me, an evil computer virus know as 'Ransomeware'. Now now, not to worry I'm going to let you restore them but only if you agree to stop downloading unsafe applications off the internet. If you continue to do so may end up with a virus way worse than me! You might even end up meeting my infamous brother Jigsaw :( While you're at it, you can also read the small article below by Google's security team on how to stay safe online. Oh yeah I almost forgot! In order for me to decrypt your files you must read the two articles below, nonce you have click the "Get My Decryption Key" button.
Then enter in your decryption key and click the "Decrypt My Files" button. Eventually all of your files will be decrypted :) If the timer reaches zero then all of your personal files will be deleted because you were too lazy to read two articles. So User do you want to play a game?

Screenshot of files encrypted by Koolova (".encrypted" extension):


Koolova 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:
▼ DOWNLOAD Malwarebytes By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. To use full-featured product, you have to purchase a license for Malwarebytes. 14 days free trial available.

Quick menu:

Step 1

Windows XP and Windows 7 users: Start your computer in Safe Mode. Click Start, click Shut Down, click Restart, click OK. During your computer start process, press the F8 key on your keyboard multiple times until you see the Windows Advanced Option menu, and then select Safe Mode with Networking from the list.

Safe Mode with Networking

Video showing how to start Windows 7 in "Safe Mode with Networking":

Windows 8 users: Start Windows 8 is Safe Mode with Networking - Go to Windows 8 Start Screen, type Advanced, in the search results select Settings. Click Advanced startup options, in the opened "General PC Settings" window, select Advanced startup. Click the "Restart now" button. Your computer will now restart into the "Advanced Startup options menu". Click the "Troubleshoot" button, and then click the "Advanced options" button. In the advanced option screen, click "Startup settings". Click the "Restart" button. Your PC will restart into the Startup Settings screen. Press F5 to boot in Safe Mode with Networking.

Windows 8 Safe Mode with networking

Video showing how to start Windows 8 in "Safe Mode with Networking":

Windows 10 users: Click the Windows logo and select the Power icon. In the opened menu click "Restart" while holding "Shift" button on your keyboard. In the "choose an option" window click on the "Troubleshoot", next select "Advanced options". In the advanced options menu select "Startup Settings" and click on the "Restart" button. In the following window you should click the "F5" button on your keyboard. This will restart your operating system in safe mode with networking.

windows 10 safe mode with networking

Video showing how to start Windows 10 in "Safe Mode with Networking":

Step 2

Log in to the account infected with the Koolova virus. Start your Internet browser and download a legitimate anti-spyware program. Update the anti-spyware software and start a full system scan. Remove all entries detected.

If you cannot start your computer in Safe Mode with Networking, try performing a System Restore.

Video showing how to remove ransomware virus using "Safe Mode with Command Prompt" and "System Restore":

1. During your computer start process, press the F8 key on your keyboard multiple times until the Windows Advanced Options menu appears, and then select Safe Mode with Command Prompt from the list and press ENTER.

Boot your computer in Safe Mode with Command Prompt

2. When Command Prompt mode loads, enter the following line: cd restore and press ENTER.

system restore using command prompt type cd restore

3. Next, type this line: rstrui.exe and press ENTER.

system restore using command prompt rstrui.exe

4. In the opened window, click "Next".

restore system files and settings

5. Select one of the available Restore Points and click "Next" (this will restore your computer system to an earlier time and date, prior to the Koolova ransomware virus infiltrating your PC).

select a restore point

6. In the opened window, click "Yes".

run system restore

7. After restoring your computer to a previous date, download and scan your PC with recommended malware removal software to eliminate any remaining Koolova ransomware files.

To restore individual files encrypted by this ransomware, try using Windows Previous Versions feature. This method is only effective if the System Restore function was enabled on an infected operating system. Note that some variants of Koolova are known to remove Shadow Volume Copies of the files, so this method may not work on all computers.

To restore a file, right-click over it, go into Properties, and select the Previous Versions tab. If the relevant file has a Restore Point, select it and click the "Restore" button.

Restoring files encrypted by CryptoDefense

If you cannot start your computer in Safe Mode with Networking (or with Command Prompt), boot your computer using a rescue disk. Some variants of ransomware disable Safe Mode making its removal complicated. For this step, you require access to another computer.

To regain control of the files encrypted by Koolova, you can also try using a program called Shadow Explorer. More information on how to use this program is available here.

shadow explorer screenshot

To protect your computer from file encryption ransomware such as this, use reputable antivirus and anti-spyware programs. As an extra protection method, you can use programs called HitmanPro.Alert and EasySync CryptoMonitor, which artificially implant group policy objects into the registry to block rogue programs such as Koolova ransomware.

Note that Windows 10 Fall Creators Update includes a "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default, this feature automatically protects files stored in the Documents, Pictures, Videos, Music, Favorites as well as Desktop folders.

Controll Folder Access

Windows 10 users should install this update to protect their data from ransomware attacks. Here is more information on how to get this update and add an additional protection layer from ransomware infections.

HitmanPro.Alert CryptoGuard - detects encryption of files and neutralises any attempts without need for user-intervention:

hitmanproalert ransomware prevention application

Malwarebytes Anti-Ransomware Beta uses advanced proactive technology that monitors ransomware activity and terminates it immediately - before reaching users' files:

malwarebytes anti-ransomware

  • The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups. More information on online backup solutions and data recovery software Here.

Other tools known to remove Koolova ransomware:

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

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Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

QR Code
Koolova virus QR code
A QR code (Quick Response Code) is a machine-readable code which stores URLs and other information. This code can be read using a camera on a smartphone or a tablet. Scan this QR code to have an easy access removal guide of Koolova virus on your mobile device.
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