Remove Kronos ransomware from the operating system

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

Kronos ransomware removal instructions

What is Kronos?

Kronos is malicious software and a new variant of Ouroboros ransomware. It is designed to encrypt data and demand ransom payments for its recovery (i.e., payment for decryption tools/software). During the encryption process, all files are appended with the ransomware developer's email address, victim's unique ID number, and ".KRONOS" extension (format: ".Email=[]ID=[victim's_ID].KRONOS"). Therefore, "1.jpg might be renamed to a filename such as "1.jpg.Email=[]ID=[ALEohfnsVHCbRp8].KRONOS". Once this process is complete, a text file called "HowToDecrypt.txt" is stored in every affected folder.

The text file contains the ransom message, which states that all files have been encrypted and victims must pay if they wish to decrypt them. It gives instructions about how to accomplish this. Firstly, users are to contact the cyber criminals behind Kronos, via the email address provided. Their email must include the unique ID (which each encrypted file contains in the title) or the "HowToDecrypt.txt" file. As 'proof' of their ability to restore data, the criminals offer to decrypt one file free of charge. This must be no larger than 1 MB and contain no 'valuable information' (e.g. database, backup, or excel sheet). The ransom size is not stated, however, the chosen currency is the Bitcoin cryptocurrency. After the transaction is made, victims are promised tools, which will supposedly decrypt their data. They are also warned not to attempt to decrypt files with third party software and/or other recovery tools, since this will result in permanent data damage. The ransom message is ended with links to web pages, which detail how to purchase Bitcoins. Typically, ransomware-type programs use strong encryption, which cannot be broken without the involvement of the people who encrypted the files. Regardless, do not meet the ransom demands or communicate with any cyber criminals. Despite paying, many victims receive no decryption tools/software, thereby leaving their data encrypted and useless. Removing this malicious program will not restore the affected files, however, it will prevent Kronos from further data encryption. The only solution is to recover data from a backup, provided one was made prior to the infection and kept separately.

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

Kronos decrypt instructions

ElderDEADMIN LOCKER, and oo7 are just some examples of ransomware infections similar to Kronos. In fact, all malware of this type shares key traits: they encrypt data and demand payments. Main differences include cryptographic algorithm used (symmetric or asymmetric) and size of ransom. Usually, the latter ranges between three-digit and four-digit sums. Digital currencies (e.g. cryptocurrencies, pre-paid vouchers, etc.) are preferred by cyber criminals, as these transactions are difficult/impossible to trace, unless the ransomware is still in development and/or has certain flaws/bugs - manual decryption (without the involvement of cyber criminals) is not possible. To protect files against data encryption and damaging infections, keep backups on remote servers and/or unplugged storage devices. These are also liable to damage, and so you should store multiple backup copies in different locations.

How did ransomware infect my computer?

Ransomware and other malware is mostly proliferated through spam campaigns, trojans, untrustworthy download channels, fake software updaters and "cracking" (activation) tools. Thousands of deceptive emails are sent out using spam campaigns. These emails are frequently highlighted as "important", "official", "urgent" or otherwise marked as priority mail. They contain infectious attachments (or web-links leading to them) and can be in various file formats (e.g. archive and executable files, PDF and Microsoft Office documents, JavaScript, etc.). Once the files are run, executed, or opened in other ways, they cause infection by downloading/installing malicious software. Trojans are malware infections, which operate by causing chain infections. Peer-to-Peer sharing networks (BitTorrent, eMule, Gnutella, etc.), unofficial and free file-hosting websites, third party downloaders are classed as untrustworthy and more likely to offer deceptive or bundled content. By exploiting weaknesses of outdated programs, fake updaters cause infections, however, they can simply download/install malicious software rather than the promised updates. Illegal software activation tools ("cracks") often download/install malware, rather than activating the chosen products.

Threat Summary:
Name Kronos virus
Threat Type Ransomware, Crypto Virus, Files locker.
Encrypted Files Extension .KRONOS (this ransomware also appends filenames with the victim's unique ID and developer's email address).
Ransom Demanding Message HowToDecrypt.txt
Cyber Criminal Contact
Detection Names Avast (Win32:RansomX-gen [Ransom]), BitDefender (DeepScan:Generic.Ransom.Ouroboros.8663), ESET-NOD32 (A Variant Of Win32/Filecoder.Ouroboros.D), Kaspersky (Trojan-Ransom.Win32.Crypren.afyf), Full List Of Detections (VirusTotal)
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.
Distribution methods Infected email attachments (macros), torrent websites, malicious ads.
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)

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How to protect yourself from ransomware infections?

Irrelevant and suspicious emails should not be opened, especially those received from unknown senders (addresses). Any attachments found in these emails must never be run, executed, or otherwise opened. The same extends to web-links listed in these deceptive emails - they must not be clicked. Opening dangerous attachments will initiate download/installation of malware. Use only official and verified download sources. Various sharing networks and third party downloaders can offer malicious software disguised as legitimate products and/or normal programs bundled with malware. Software should be activated and updated via tools/functions provided by the genuine developers, and not using "cracking" tools or third party updaters. Have a reputable anti-virus/anti-spyware suite installed and kept up-to-date. This software should be used to perform regular system scans and removal of potential threats. If your computer is already infected with Kronos, we recommend running a scan with Malwarebytes for Windows to automatically eliminate this ransomware.

Text presented in Kronos ransomware text file ("HowToDecrypt.txt"):

Your Files Have Been Encrypted

If You Need Your Files You Should Pay Decryption Price

The Steps For Getting Decryption Tool :

1-Send Id On The Files Or  HowtoDecrypt.txt Files to Our Email

2-Send 1MB File For Getting Decryption Test to Make Sure You Can Get Your Files Back With Us(The Test File Should Not Contain Valuable Data Like Databases Excel Sheets or Backups)

3- Pay Decryption Price ( Payment Should Be With Bitcoin )

4- Get Decryption Tool With Key


Using 3rd Party Applications or  Recovery Tools May Damage Your Files permanetly

 Your ID :-
 Our Email:

 You Can Learn How to Buy Bitcoin From This links Below



Screenshot of files encrypted by Kronos (".KRONOS" extension):

Files encrypted by Kronos

Kronos 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:
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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 Kronos 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 Kronos 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 Kronos 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 Kronos 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 Kronos, 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 Kronos 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, and 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 Kronos 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 since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

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Removal Instructions in other languages
Malware activity

Global malware activity level today:

Medium threat activity

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

QR Code
Kronos 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 Kronos virus on your mobile device.
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