RYUK Ransomware

Also Known As: RYUK virus
Distribution: Moderate
Damage level: Severe

RYUK ransomware removal instructions

What is RYUK?

RYUK is a high-risk ransomware-type virus that infiltrates the system and encrypts most stored data, thereby making it unusable. Due to its similarities with Hermes ransomware, there is a high probability that these two viruses have the same developer. Unlike most other viruses, this malware does not rename or append any extension to encrypted files. It is, however, worth noting that updated variant of RYUK ransomware (titled RYK ransomware) appends .RYK extension (thus, its name). RYUK is also designed to create a text file ("RyukReadMe.txt"), placing a copy in every existing folder.

As usual, the new text file delivers a message that informs victims of the encryption and encourages them to pay a ransom to restore their data. Be aware that RYUK uses RSA-4096 and AES-256 encryption algorithms. Therefore, each victim receives several unique keys that are necessary to restore data. Cyber criminals hide all keys on a remote server. Restoring data without these keys is impossible, and each victim is forced to pay a ransom in exchange for their release. The cost is not confirmed - all information is provided via email, however, the size of ransoms varies with each victim. It is also stated that, for each day of delay, the victim must pay an additional .5 Bitcoin (currently equivalent to ~$3200). As compared to other ransomware-type viruses, this cost is high - it typically fluctuates between $500 and $1500 (and it usually does not increase). Note that RYUK is designed to target large companies and infect many computers at once. Although paying thousands of dollars for everyday users might seem too much, large companies often agree, since their encrypted data is often much more valuable. Despite this, and no matter what the cost, it is advised not to pay. Ransomware developers often ignore victims once payments are submitted. Paying often gives no positive result and users are scammed. Therefore, you are advised to ignore all requests to contact developers or pay any ransom. Unfortunately, there are no tools capable of cracking RSA/AES encryption and restoring data free of charge. The only solution is to restore everything from a backup.

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

RYUK decrypt instructions

There are dozens of viruses that share similarities with RYUK. The list of examples includes (but is not limited to) FOX, ShutUpAndDance, PGPSnippet, and Princess. Although these viruses are developed by different cyber criminals, their behavior is identical - all encrypt data and make ransom demands. In most cases, ransomware-type viruses have just two major differences: size of ransom and type of encryption algorithm used. Unfortunately, most employ algorithms that generate unique decryption keys. Therefore, unless the virus is not fully developed or has certain bugs/flaws, restoring data manually without involvement of developers (contacting these people is not recommended) is impossible. RYUK and other similar viruses present a strong case for maintaining regular data backups, but remember to store them on a remote server or unplugged storage device. If not, malware will encrypt backups together with regular files.

How did ransomware infect my computer?

To proliferate ransomware, developers often use trojans, spam emails, peer-to-peer (P2P) networks, unofficial software download sources, and fake software updaters. Trojans open "backdoors" for other viruses to infiltrate the system. Spam emails are delivered with malicious attachments that, once opened, download and install viruses. P2P networks and other third party download/installation sources (freeware download websites, free file hosting sites, etc.) present malware as legitimate software, thereby tricking users into downloading and installing viruses. Fake updaters infect the system by exploiting outdated software bugs/flaws or simply downloading and installing malware rather than updates.

Threat Summary:
Name RYUK virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension Updated variant of RYUK ransomware appends .RYK extension.
Ransom Demanding Message RyukReadMe.txt
Cyber Criminal Contact eliasmarco@tutanota.com, camdenScott@protonmail.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.
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)

To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Malwarebytes.
▼ Download Malwarebytes
To use full-featured product, you have to purchase a license for Malwarebytes. 14 days free trial available.

How to protect yourself from ransomware infections?

The main reasons for computer infections are poor knowledge and careless behavior. Therefore, pay close attention when browsing the Internet and downloading/installing/updating software. Think twice before opening email attachments. Irrelevant files and those received from suspicious/unrecognizable email addresses should never be opened. Furthermore, download software from official sources only, using direct download links. Third party downloaders/installers often include rogue apps, and thus should never be used. The same rule applies to software updates. It is important to keep installed applications up-to-date, however, this should be achieved only through implemented functions or tools provided by the official developer. Having a reputable anti-virus/anti-spyware suite installed and running is also essential. The key to computer safety is caution. If your computer is already infected with RYUK, we recommend running a scan with Malwarebytes for Windows to automatically eliminate this ransomware.

Text presented in RYUK ransomware text file ("RyukReadMe.txt"):


Your business is at serious risk.
There is a significant hole in the security system of your company.
We've easily penetrated your network.
You should thank the Lord for being hacked by serious people not some stupid schoolboys or dangerous punks.
They can damage all your important data just for fun.

Now your files are crypted with the strongest millitary algorithms RSA4096 and AES-256.
No one can help you to restore files without our special decoder.

Photorec, RannohDecryptor etc. repair tools
are useless and can destroy your files irreversibly.

If you want to restore your files write to emails (contacts are at the bottom of the sheet)
and attach 2-3 encrypted files
(Less than 5 Mb each, non-archived and your files should not contain valuable information
(Databases, backups, large excel sheets, etc.)).
You will receive decrypted samples and our conditions how to get the decoder.
Please don't forget to write the name of your company in the subject of your e-mail.

You have to pay for decryption in Bitcoins.
The final price depends on how fast you write to us.
Every day of delay will cost you additional +0.5 BTC
Nothing personal just business

As soon as we get bitcoins you'll get all your decrypted data back.
Moreover you will get instructions how to close the hole in security
and how to avoid such problems in the future
+ we will recommend you special software that makes the most problems to hackers.

Attention! One more time !

Do not rename encrypted files.
Do not try to decrypt your data using third party software.

P.S. Remember, we are not scammers.
We don`t need your files and your information.
But after 2 weeks all your files and keys will be deleted automatically.
Just send a request immediately after infection.
All data will be restored absolutely.
Your warranty - decrypted samples.

contact emails

BTC wallet:


No system is safe

Screenshot of files encrypted by RYUK (no extension):

Files encrypted by RYUK

Update November 6, 2019 - RYUK ransomware has been recently updated and implemented with two new features, which allow it to encrypt drives connected to the same LAN network and even infect machines that are in sleep/standby mode. To achieve this, RYUK employs Address Resolution Protocol (ARP) and Wake-on-LAN utility. Note that RYUK is developed to work only on Windows-based machines. However, its ability to access drives connected to the LAN network increases RYUK's damage level dramatically, due to the fact that it can encrypt files no matter what operating system another machine is running. In other words, although RYUK ransomware is designed to run only in Windows operating systems, it also poses threat to Linux, MacOS, and other operating systems as well, if they're connected to the same LAN network as the infected Windows machine. The ransomware will simply remotely access data and encrypt it without infiltrating into other machines. You can find more information about these new features in this Threatpost article.

Update December 27, 2019 - RYUK's developers released yet another variant of this ransomware which is designed to skip *NIX-type folders. This file system is used in Unix-based operating systems, such as Linux. Now even though there is no existing RYUK ransomware for Unix-type operating systems, there are scenarios where this ransomware can gain access to these systems while encrypting data in Windows OS.

Update January 27, 2020 - In September, 2019 cyber criminals released a new version of RYUK ransomware which was designed to steal data before encrypting. On its initial release this version was stealing only Microsoft Word (".docx") and Excel (".xlsx") files. However, last week an a new variant of this "updated" RYUK ransomware was discovered and it turns out that the list of targeted data types has increased - it now includes various image files, as well as cryptocurrency wallets. However, it is worth noting that the malware doesn't simply steal all the existing documents of the targeted type. Instead, it scans documents' names and searches for specific strings and, if the name contains a certain string, it will be uploaded to a remote server controlled by cyber criminals. It is also unconfirmed whether this updated RYUK ransomware was released by its official developers or if someone has simply "borrowed" the source code. Either way, the end result may is still the same. You can find more information regarding this stealer in Lawrence Abrams' article on Bleeping Computer.

List of file formats targeted by data-stealing RYUK malware:

  • .cpp
  • .doc
  • .docx
  • .h
  • .jpg
  • .pdf
  • .xls
  • .xlsx
  • wallet.dat

RYUK 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 RYUK 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 RYUK 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 RYUK 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 RYUK 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 RYUK, 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 RYUK 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 RYUK 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.

Our malware removal guides are free. However, if you want to support us you can send us a donation.

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
RYUK 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 RYUK virus on your mobile device.
We Recommend:

Get rid of Windows malware infections today:

Download Malwarebytes

Platform: Windows

Editors' Rating for Malwarebytes:
Editors ratingOutstanding!

[Back to Top]

To use full-featured product, you have to purchase a license for Malwarebytes. 14 days free trial available.