Ryuk ransomware removal and files decryptor [upd. November 2019]

Posted on November 1, 2019

9 min read

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It’s not by chance that the Ryuk ransomware is considered one of a kind, so here are the whys plus how-to’s regarding the way to remove it and restore data.

[November 2019 update]

What is Ryuk ransomware?
Ryuk ransomware automated removal and data decryptor
Ryuk ransomware manual removal and file decryption
Ransomware Prevention Tips

What is Ryuk ransomware?

Quite a bit of the expert discussion about the Ryuk ransomware echoes ambiguity and has a flavor of speculations and rumors. This relatively new piece of file-encrypting code was first documented in late summer last year, when it hit merely a few companies but made the executives cough up more than half a million USD worth of Bitcoin. Now in 2019, the strain appears to have matured, at least in terms of the distribution methods and a wider range of targets. Given the codebase affinity with another sample called Hermes, which is known to hail from North Korea, Ryuk is said to have the same origin. Some analysts have a separate opinion on this matter, stating that the baddie stems from Russia. One way or another, it is a serious headache – not really for regular users, though. The victims are high-profile organizations, including major newsprint media firms in the U.S., cloud hosting providers, and even critical infrastructure, such as water supply services.

The verbose copy of ransom note dropped by Ryuk ransomware

Obviously, targets as big as that are the perfect object of extortion. This explains the immense amounts of cryptocurrency funneling towards the crooks. After the attack takes place through a technique that will described further down, the Ryuk virus moves laterally inside the network to infect all the other hosts on it. The predatory program disables VSS (Volume Shadow Copy Service) and prevents the user from restoring their system to an earlier state. It also scans the local disks, external repositories if plugged in, as well as network drives in search of valuable files.

Each item spotted during this routine then undergoes strong encryption. The filenames are appended with the .ryk extension as a telltale sign of which objects has been crippled on the computer. Next comes the pressure and extortion part of the raid. The dodgy entity drops a combo of ransom alerts that differ in their wording and tone, yet convey basically the same message. While both of them are named RyukReadMe.txt, one is quite verbose and makes an even mannerly impression (see image above).

RyukReadMe.txt ransom note edition doesn’t go into as much detail as its ‘well-mannered’ counterpart

The “extended” edition of the criminals’ message emphasizes that every day of nonpayment will result in the increment of the ransom size by 0.5 BTC. To top it off, if two weeks elapse and the felons don’t get what they want, they threaten to erase the private decryption keys and thereby make it impossible to reinstate anything. To avoid that, the plagued user is coerced to shoot a message to eliasmarco@tutanota.com or CamdenScott@protonmail.com, where they should indicate the name of the company and attach a couple of files under 5 MB each that aren’t particularly important. The malefactors will supposedly restore these several items and send them back to the victim along with the concise conditions on how to obtain the decryptor.

The other copy of the ransom note highlights what has happened and how to sort it out in a brief fashion. It says, “Your network has been penetrated”, stresses the futility of commonplace file recovery attempts and instructs the victim to contact the cyber racketeers at AndyMitton@protonmail.com or AndyMitton@tutanota.com.

Speaking of the propagation, the Ryuk ransomware operators have a number of furtive, highly effective mechanisms on their hands. One is all about the use of botnets, where the file-encrypting component poses as a secondary payload dropped alongside a data-stealing virus, such as TrickBot. One more infection vector engages phishing or its peculiar type known as spear-phishing, which fully aligns with the targeted essence of Ryuk’s incursions. Yet another tactic up the crooks’ sleeve has to do with compromising remote desktop services. This mashup of different distribution practices allows the perpetrators to sting exactly where the weak links in target organizations’ security are at. Such as modus operandi, apparently, presupposes that some reconnaissance be done prior to deploying the onslaught.

Once the initial stage of the intrusion has been carried out, Ryuk takes advantage of Remote Desktop Protocol to move laterally within the breached network. This process goes on until the attackers get enough privileges to access the domain controller. From there, the crooks use PsExec utility to deliver the harmful executable to all the hosts constituting the enterprise environment. Another element of the offensive involves batch scripts the ransomware operators run remotely. Their objective is to terminate certain services, including security software and IPS (intrusion prevention systems), which may undermine the attack progress. Batch commands are also leveraged to wipe data backups so that the ransom is the only way to restore files after the malicious encryption is performed.

If an enterprise network is immobilized due to such an interference propped by crypto, chances are the ransom is the only viable response if the hostage data really matters to keep the business up and running. This was the case with the Ryuk ransomware attacking three healthcare facilities in Alabama in early October 2019. In light of a complete shutdown of the affected hospitals’ computer systems, the local health services officials were forced to pay an undisclosed amount of ransoms. In some cases, though, a few forensic techniques may help address the predicament partially or fully. Anyway, the tips below can turn out to be worthwhile in the Ryuk ransomware attack scenario, so peruse the follow-up sections and see what can be done beyond interaction with the cybercriminals.

Ryuk ransomware automated removal and data recovery

When faced with ransomware like Ryuk, one of the best shortcuts in terms of removal is to use Combo Cleaner, a lightweight and incredibly effective application with PC security and optimization features under the hood. It detects and thoroughly deletes threats while giving you insights into the overall health of your computer.

This program’s protection power spans modules that forestall all known types of malware, including ransomware and browser hijackers, and take your online security to the next level by blocking phishing sites and other suspicious web pages. Follow these simple steps to eliminate the infection for good:

1. Download Combo Cleaner installer.

Download Ryuk remover

^{Combo Cleaner scans your PC with no strings attached, but you’ll have to buy its fully functional version to remove the threats it detects. The disk optimization tools that find large files and duplicates are free to use.}

2. Open the CCSetup.exe file to get started. Several subsequent screens will allow you to make initial customizations so that the program works exactly as you need from the get-go.

3. The installation will be followed by an update of malware signatures. Once this process is through, click the Start Scan button in the left-hand sidebar.

4. Combo Cleaner will then check system locations that are most often polluted by Windows malware. The first scan can take a while to finish.

5. Combo Cleaner will display a system tray notification as soon as the scan is over. Click the Resolve found threats button to view the results.

6. The scan summary shows the names and types of the detected threats as well as their statuses and locations. Click the Remove all threats button and follow further on-screen prompts to get rid of these items.

Data recovery toolkit to the rescue

Some strains of ransomware are known to delete the original files after the encryption routine has been completed. As hostile as this activity appears, it can play into your hands. There are applications designed to revive the information that was obliterated because of malfunctioning hardware or due to accidental removal. The tool called Stellar Data Recovery features this type of a capability and therefore it can be applied in ransom attack scenarios to at least get the most important files back. So use the app to get an idea of what data can be restored and let it do the recovery job. Here is a step-by-step walkthrough:

1. Download and install Stellar Data Recovery.

Download Stellar Data Recovery

2. Open the application, select the types of recoverable files to look for, and click Next.

3. Choose the areas you want the tool to recover from and click the Scan button.

4. Having scanned the specified locations, the program will display a notification about the total amount of recoverable data. Close the dialog and click the Recover button. This will hopefully help you get some of your valuable files back.

Ryuk ransomware manual removal and file recovery

Some ransomware strains terminate themselves after completing the encryption job on a computer, but some don’t. Furthermore, the Ryuk virus may prevent victims from using popular antimalware tools in order to stay on board for as long as possible. Under the circumstances, it may be necessary to utilize the Safe Mode with Networking or System Restore functionality.

Remove Ryuk ransomware using Safe Mode with Networking

Get rid of Ryuk ransomware using System Restore

System Restore enables Windows users to roll back all changes made to the OS since the latest restore point creation time. This feature can help eliminate the most persistent ransomware. Before going this route, though, make sure System Restore had been enabled prior to the breach, otherwise the method will be inefficient.

Open Windows Advanced Options Menu as described in the previous section: hit F8 repeatedly when the PC is starting up. Use arrow keys to highlight the Safe Mode with Command Prompt entry. Hit Enter.
In the Command Prompt window, type cd restore and hit Enter
Type rstrui.exe in the new command line and press Enter
When the System Restore screen pops up, click Next, select a restore point that predates the contamination, and use the application’s controls to roll back the system to this earlier state.

Be advised that even after the ransomware is removed, files will still be encrypted and inaccessible. The malicious code cleanup part, however, is important because it keeps a relapse of the infection from occurring further on and eliminates all opportunistic malware.

Ways of non-ransom recovery of .ryk files encrypted by Ryuk virus

Cracking the crypto used by this ransom Trojan is more of a science fiction thing rather than an attainable prospect for the masses. This is why the troubleshooting in predicaments of this sort is a matter of two approaches: one is to pay the ransom, which isn’t an option for many victims; and the other is to apply instruments that take advantage of the ransomware’s possible weaknesses. If the latter is your pick, the advice below is a must-try.

Backups can make your day

Not only are you a lucky person in case you’ve been backing up your most important files, but you’re also a wise and prudent user. This isn’t necessarily a resource-heavy activity these days – in fact, some providers of online services are allocating a sufficient size of cloud storage space for free so that every customer can easily upload their critical data without paying a penny. Having removed the Ryuk ransomware, therefore, all you have to do is download your stuff from the remote server or transfer it all from an external piece of hardware if that’s the case.

Restore previous versions of encrypted files

A positive upshot of using this technique depends on whether or not the ransomware has erased the Volume Shadow Copies of the files on your PC. This is a Windows feature that automatically makes and keeps the backups of data elements on the hard drive as long as System Restore is enabled. The cryptoware in question is programmed to switch off the Volume Shadow Copy Service (VSS), but it has reportedly failed to in some cases.

Checking one’s options regarding this workaround is doable in two ways: through the Properties menu of each file or by means of the remarkable open-source tool called Shadow Explorer. We recommend the software-based way because it’s automated, hence faster and easier. Just install the app and use its intuitive controls to get previous versions of the encrypted objects reinstated.

Alternatively, you can leverage the Previous Versions feature, which is native to Windows operating system. This method is more cumbersome that the use of ShadowExplorer, but it can help restore the most important individual files on condition that the ransomware failed to disable the Volume Snapshot Service on the computer. Right-click on a file of choice and select Properties. Then, go to the Previous Versions tab as illustrated below.

Go ahead and pick the file’s latest backup version on the list. Use the Copy or Restore buttons to reinstate this object to a new path or to its original folder, respectively.

Ransomware Prevention Tips

To avoid Ryuk ransomware and other file-encrypting infections in the future, follow several simple recommendations:

Toggle your email provider’s anti-spam settings to filter out all the potentially harmful incoming messages. Raising the bar beyond the default protection is an important countermeasure for ransom Trojans
Define specific file extension restrictions in your email system. Make sure that attachments with the following extensions are blacklisted: .js, .vbs, .docm, .hta, .exe, .cmd, .scr, and .bat. Also, treat ZIP archives in received messages with extreme caution
Rename the vssadmin.exe process so that ransomware is unable to obliterate all Shadow Volume Copies of your files in one shot
Keep your Firewall active at all times. It can prevent crypto ransomware from communicating with its C&C server. This way, the threat won’t be able to obtain cryptographic keys and lock your files
Back up your files regularly, at least the most important ones. This recommendation is self-explanatory. A ransomware attack isn’t an issue as long as you keep unaffected copies of your data in a safe place
Use an effective antimalware suite. There are security tools that identify ransomware-specific behavior and block the infection before it can do any harm.

These techniques are certainly not a cure-all, but they will add an extra layer of ransomware protection to your security setup.

Revise your security status

Post-factum assessment of the accuracy component in malware removal scenarios is a great habit that prevents the comeback of harmful code or replication of its unattended fractions. Make sure you are good to go by running an additional safety checkup. Another benefit of using the antimalware tool is that it will keep ransomware threats from intruding on your computer further on.

Download Ryuk removal tool

FAQ

What is the RYUK virus?

RYUK is a strain of file-encrypting ransomware discovered in August 2018. It is reportedly based on the source code of a ransom Trojan called Hermes, whose development is attributed to a high-profile cybercriminal group operating from North Korea. Unlike its probable prototype that fits the mold of mainstream ransomware, RYUK specifically targets enterprise networks.

The symptoms of this attack include the .ryk extension being concatenated to encrypted files, as well as ransom notes named RyukReadMe.txt. The attackers’ demands depend on the size of the breached organization and range between 15-50 Bitcoin. In September-October 2019, the extortionists perpetrated a number of successful attacks against healthcare industry entities in the United States and Australia, some of the victims having agreed to redeem their records by sending the hefty amounts of cryptocurrency to the malefactors.

RYUK ransomware is making the rounds mainly via spear-phishing emails and RDP compromise. Across all of the reported incidents, the infection is accompanied by a payload for TrickBot, a modular Windows banking Trojan featuring extensive info-theft capabilities. Once inside, the combo spreads laterally throughout the host environment and thus infects most machines on the same network.

Does ransomware steal data?

The original objective of “classic” ransomware is to lock down valuable data and hold it for ransom. Whereas info-stealing capabilities aren’t part of this mission, some specimens are distributed along with follow-up malware that usually comes as a secondary payload. This way, the criminals can monetize their attack even if the victim refuses to cough up the ransom. For instance, Ryuk ransomware is known to propagate in tandem with a banking Trojan called TrickBot that harvests financial records belonging to a contaminated enterprise entity. Some lineages are equipped with reconnaissance components that scan the host network for specific types of data based on predefined keywords.

As soon as sensitive information is spotted, the malicious code invokes a command entailing its exfiltration to a crooks-controlled C2 server. Cybercriminal groups can benefit from the stolen data by obtaining unauthorized access to victims’ bank accounts, or they can resell trade secrets to interested parties.

What is the most common way in which user gets infected with ransomware?

Malspam (malicious spam) is the most frequently encountered attack vector. In this scenario, falling victim to ransomware is typically a matter of opening a contagious file attached to a booby-trapped email. These enclosed objects are mostly disguised as regular documents but are actually JavaScript (.js) entities or executable (.exe) files that instantly trigger the attack chain once opened.

In many cases, the attackers exploit dodgy Word macros that go with benign-looking email attachments. Once an unsuspecting recipient enables macros as the prompt tells them to, a furtive VBA (Visual Basic for Applications) is fired up to download the ransomware from the criminals’ server. This mechanism ensures that the original message slips under the radar of email filters, given that the whole malicious routine takes place at a later point.

A more refined type of this hoax is spear-phishing, a technique mainly used in targeted attacks backed by previously conducted OSINT (open-source intelligence). Similarly to spam-based incursions, this method relies on email as the contagion. The difference is that the messages are adjusted to align with the would-be victim’s occupation or interests to instill trust.

The less common distribution techniques include exploit kits and rogue software installers. RDP compromise is yet another entry point, but it is mostly used in targeted onslaughts against organizations rather than individual users.