Rhysida (.rhysida) ransomware virus – removal and decryption options

Also Known As: Rhysida virus
Damage level: Severe

What kind of malware is Rhysida?

Rhysida is the name of a ransomware-type program. It is designed to encrypt data and demand payment for its decryption.

On our testing machine, Rhysida encrypted files and appended their filenames with a ".rhysida" extension. To elaborate, a file originally named "1.jpg" appeared as "1.jpg.rhysida", "2.png" as "2.png.rhysida", and so on for all of the affected files.

After the encryption process was finished, this ransomware created a ransom note titled "CriticalBreachDetected.pdf". The message therein clearly indicated that Rhysida targets companies rather than home users.

Screenshot of files encrypted by Rhysida ransomware:

Files encrypted by Rhysida ransomware (.rhysida extension)

Ransom note overview

Rhysida's ransom note takes an uncommon spin, wherein the attackers present themselves as a "cybersecurity team" offering aid with the security breach experienced by the victim's company. The message states that confidential data has been stolen from the compromised network.

Supposedly, the company's security can be restored with the unique key developed by the "cybersecurity team". What the note actually means by this is that the encrypted files can only be unlocked with the decryption key possessed by the cyber criminals. The victim is warned against attempting manual decryption since that may result in permanent data loss.

Additionally, when the message details the potential ramifications of the data exfiltration (e.g., leaking, sale to media or competitors, etc.) – that is actually a threat intended to push the victim into complying with the attackers' demands.

Rhysida ransomware overview

Based on our considerable experience researching ransomware infections, we can conclude that decryption is rarely possible without the cyber criminals' involvement. Despite this, we strongly advise against meeting the ransom demands. Although paid – criminals often do not send the promised decryption keys/tools.

To prevent Rhysida ransomware from encrypting more files – it must be removed from the operating system. Unfortunately, removal will not restore already affected data. The only solution is to recover the files from a backup (if one was created prior and is stored elsewhere).

The general advice for ensuring data safety is to keep backups in multiple separate locations, such as remote service, unplugged storage devices, and others.

Ransomware examples

HavocTnwkgbvlAnti-usDARKKUR, and WAGNER are merely some examples of ransomware we have analyzed recently. This software operates practically the same throughout (i.e., it encrypts files and makes ransom demands for decryption).

However, ransomware-type programs have two major differences in-between – the cryptographic algorithms they use (symmetric or asymmetric) and the ransom size. The sums can vary drastically (from 3 to 8 digits in USD) depending on the intended victim, i.e., home user vs. large entity (e.g., company, organization, institution, etc.).

How did ransomware infect my computer?

Malware (ransomware included) is proliferated predominantly by employing phishing and social engineering tactics. It is commonly disguised as or bundled with regular programs/media.

Virulent files can be archives (RAR, ZIP, etc.), executables (.exe, .run, etc.), documents (Microsoft Office, Microsoft OneNote, PDF, etc.), JavaScript, and so forth. Once an infectious file is opened – the malware download/installation process is triggered.

The most widely used distribution methods include: malicious attachments and links in spam mail (e.g., email, PM/DM, SMS, etc.), untrustworthy download channels (e.g., unofficial and freeware websites, Peer-to-Peer sharing networks, etc.), drive-by (stealthy/deceptive) downloads, illegal software activation tools ("cracks"), fake updates, online scams, and malvertising.

Furthermore, some malicious programs can self-spread through local networks and removable storage devices (e.g., external hard drives, USB flash drives, etc.).

Threat Summary:
Name Rhysida virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .rhysida
Ransom Demanding Message CriticalBreachDetected.pdf
Free Decryptor Available? Partial (more information below)
Cyber Criminal Contact ChantellGrant@onionmail.org, LorriBuckridge@onionmail.org
Detection Names Avast (Win32:Dh-A [Heur]), Combo Cleaner (Trojan.GenericKD.67412686), ESET-NOD32 (A Variant Of Win64/Filecoder.IN), Kaspersky (Trojan-Ransom.Win32.Encoder.ucn), Microsoft (Program:Win32/Wacapew.C!ml), 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)

To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner.
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How to protect yourself from ransomware infections?

We strongly advise downloading only from official and verified sources. All programs must be activated and updated by using legitimate functions/tools, as those obtained from third-parties can contain malware.

Another recommendation is to be vigilant while browsing since fake and dangerous online content usually appears ordinary and harmless. Vigilance must be extended to incoming emails and other messages. We advise against opening attachments or links present in suspicious/irrelevant mail, as they can be malicious.

It is paramount for device and user safety to have a dependable anti-virus installed and kept up-to-date. Security software must be used to run regular system scans and to remove detected threats/issues. If your computer is already infected with Rhysida, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.

Screenshot of Rhysida ransomware's ransom note ("CriticalBreachDetected.pdf"):

Rhysida ransomware ransom note (CriticalBreachDetected.pdf)

Text presented in this message:

Dear company,

This is an automated alert from cybersecurity team Rhysida. An unfortunate
situation has arisen – your digital ecosystem has been compromised, and a
substantial amount of confidential data has been exfiltrated from your network.
The potential ramifications of this could be dire, including the sale, publication,
or distribution of your data to competitors or media outlets. This could inflict
significant reputational and financial damage.

However, this situation is not without a remedy.

Our team has developed a unique key, specifically designed to restore your
digital security. This key represents the first and most crucial step in
recovering from this situation. To utilize this key, visit our secure portal:
- with your
secret key - or write email:
ChantellGrant@onionmail.org LorriBuckridge@onionmail.org

It’s vital to note that any attempts to decrypt the encrypted files independently
could lead to permanent data loss. We strongly advise against such actions.

Time is a critical factor in mitigating the impact of this breach. With each
passing moment, the potential damage escalates. Your immediate action and
full cooperation are required to navigate this scenario effectively.

Rest assured, our team is committed to guiding you through this process. The
journey to resolution begins with the use of the unique key. Together, we can
restore the security of your digital environment.

Best regards

Screenshot of Rhysida's Tor network website:

Rhysida ransomware Tor website

Video showing how to remove Rhysida ransomware using Combo Cleaner:

Update August 16, 2023 – research undertaken by the Check Point cybersecurity company has uncovered links between Rhysida and Vice Society. The latter's disappearance closely coincided with Rhysida's appearance.

Check Point's analysts found weighty evidence of their link by examining similarities between the methodologies implemented by the ransomware groups, including their shared spheres of interest (e.g., education/research, manufacturing, medical, and other sectors).

More information on this can be found in an article on the Check Point Research website.

Update February 13, 2024 – a flaw in Rhysida's encryption process has been used in private to generate viable decryptions since at least the spring of 2023. The method was successfully developed due to the ransomware encrypting files partially and leaving the rest in plaintext.

The critical flaw was detected in Rhysida's use of the random number generator (CSPRNG); hence, it was possible to recover CSPRNG's internal state and fashion the key necessary to decrypt affected data. Researchers from South Korea, including the employees of the Korean Internet & Security Agency (KISA), publicized information regarding the ransomware's weakness.

KISA has also released a free decryptor on their website. It is noteworthy that this tool may only recover data locked by the Rhysida Windows encryptor and not the PowerShell-based one or encryptions carried out on VMware ESXi. However, this decryptor's success rates and safety have not been confirmed.

More information on the flaw in Rhysida ransomware's encryption can be found in an article by Bill Toulas on the Bleeping Computer website.

Avast has also released a decryption tool capable of restoring data encrypted by Rhysida ransomware. You can download the tool and find its user manual in Avast's website.

Screenshot of Avast Rhysida decryptor:

Avast Rhysida decryptor

Rhysida ransomware removal:

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced IT skills. Combo Cleaner 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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Video suggesting what steps should be taken in case of a ransomware infection:

Quick menu:

Reporting ransomware to authorities:

If you are a victim of a ransomware attack we recommend reporting this incident to authorities. By providing information to law enforcement agencies you will help track cybercrime and potentially assist in the prosecution of the attackers. Here's a list of authorities where you should report a ransomware attack. For the complete list of local cybersecurity centers and information on why you should report ransomware attacks, read this article.

List of local authorities where ransomware attacks should be reported (choose one depending on your residence address):

Isolating the infected device:

Some ransomware-type infections are designed to encrypt files within external storage devices, infect them, and even spread throughout the entire local network. For this reason, it is very important to isolate the infected device (computer) as soon as possible.

Step 1: Disconnect from the internet.

The easiest way to disconnect a computer from the internet is to unplug the Ethernet cable from the motherboard, however, some devices are connected via a wireless network and for some users (especially those who are not particularly tech-savvy), disconnecting cables may seem troublesome. Therefore, you can also disconnect the system manually via Control Panel:

Navigate to the "Control Panel", click the search bar in the upper-right corner of the screen, enter "Network and Sharing Center" and select search result: Disconnecting computer from the Internet (step 1)

Click the "Change adapter settings" option in the upper-left corner of the window: Disconnecting computer from the Internet (step 2)

Right-click on each connection point and select "Disable". Once disabled, the system will no longer be connected to the internet. To re-enable the connection points, simply right-click again and select "Enable". Disconnecting computer from the Internet (step 3)

Step 2: Unplug all storage devices.

As mentioned above, ransomware might encrypt data and infiltrate all storage devices that are connected to the computer. For this reason, all external storage devices (flash drives, portable hard drives, etc.) should be disconnected immediately, however, we strongly advise you to eject each device before disconnecting to prevent data corruption:

Navigate to "My Computer", right-click on each connected device, and select "Eject": Ejecting external storage devices

Step 3: Log-out of cloud storage accounts.

Some ransomware-type might be able to hijack software that handles data stored within "the Cloud". Therefore, the data could be corrupted/encrypted. For this reason, you should log-out of all cloud storage accounts within browsers and other related software. You should also consider temporarily uninstalling the cloud-management software until the infection is completely removed.

Identify the ransomware infection:

To properly handle an infection, one must first identify it. Some ransomware infections use ransom-demand messages as an introduction (see the WALDO ransomware text file below).

Identify ransomware-type infection (step 1)

This, however, is rare. In most cases, ransomware infections deliver more direct messages simply stating that data is encrypted and that victims must pay some sort of ransom. Note that ransomware-type infections typically generate messages with different file names (for example, "_readme.txt", "READ-ME.txt", "DECRYPTION_INSTRUCTIONS.txt", "DECRYPT_FILES.html", etc.). Therefore, using the name of a ransom message may seem like a good way to identify the infection. The problem is that most of these names are generic and some infections use the same names, even though the delivered messages are different and the infections themselves are unrelated. Therefore, using the message filename alone can be ineffective and even lead to permanent data loss (for example, by attempting to decrypt data using tools designed for different ransomware infections, users are likely to end up permanently damaging files and decryption will no longer be possible even with the correct tool).

Another way to identify a ransomware infection is to check the file extension, which is appended to each encrypted file. Ransomware infections are often named by the extensions they append (see files encrypted by Qewe ransomware below).

Identify ransomware-type infection (step 2)

This method is only effective, however, when the appended extension is unique - many ransomware infections append a generic extension (for example, ".encrypted", ".enc", ".crypted", ".locked", etc.). In these cases, identifying ransomware by its appended extension becomes impossible.

One of the easiest and quickest ways to identify a ransomware infection is to use the ID Ransomware website. This service supports most existing ransomware infections. Victims simply upload a ransom message and/or one encrypted file (we advise you to upload both if possible).

Identify ransomware-type infection (step 3)

The ransomware will be identified within seconds and you will be provided with various details, such as the name of the malware family to which the infection belongs, whether it is decryptable, and so on.

Example 1 (Qewe [Stop/Djvu] ransomware):

Identify ransomware-type infection (step 4)

Example 2 (.iso [Phobos] ransomware):

Identify ransomware-type infection (step 5)

If your data happens to be encrypted by ransomware that is not supported by ID Ransomware, you can always try searching the internet by using certain keywords (for example, a ransom message title, file extension, provided contact emails, crypto wallet addresses, etc.).

Search for ransomware decryption tools:

Encryption algorithms used by most ransomware-type infections are extremely sophisticated and, if the encryption is performed properly, only the developer is capable of restoring data. This is because decryption requires a specific key, which is generated during the encryption. Restoring data without the key is impossible. In most cases, cybercriminals store keys on a remote server, rather than using the infected machine as a host. Dharma (CrySis), Phobos, and other families of high-end ransomware infections are virtually flawless, and thus restoring data encrypted without the developers' involvement is simply impossible. Despite this, there are dozens of ransomware-type infections that are poorly developed and contain a number of flaws (for example, the use of identical encryption/decryption keys for each victim, keys stored locally, etc.). Therefore, always check for available decryption tools for any ransomware that infiltrates your computer.

Finding the correct decryption tool on the internet can be very frustrating. For this reason, we recommend that you use the No More Ransom Project and this is where identifying the ransomware infection is useful. The No More Ransom Project website contains a "Decryption Tools" section with a search bar. Enter the name of the identified ransomware, and all available decryptors (if there are any) will be listed.

Searching for ransomware decryption tools in nomoreransom.org website

Restore files with data recovery tools:

Depending on the situation (quality of ransomware infection, type of encryption algorithm used, etc.), restoring data with certain third-party tools might be possible. Therefore, we advise you to use the Recuva tool developed by CCleaner. This tool supports over a thousand data types (graphics, video, audio, documents, etc.) and it is very intuitive (little knowledge is necessary to recover data). In addition, the recovery feature is completely free.

Step 1: Perform a scan.

Run the Recuva application and follow the wizard. You will be prompted with several windows allowing you to choose what file types to look for, which locations should be scanned, etc. All you need to do is select the options you're looking for and start the scan. We advise you to enable the "Deep Scan" before starting, otherwise, the application's scanning capabilities will be restricted.

Recuva data recovery tool wizard

Wait for Recuva to complete the scan. The scanning duration depends on the volume of files (both in quantity and size) that you are scanning (for example, several hundred gigabytes could take over an hour to scan). Therefore, be patient during the scanning process. We also advise against modifying or deleting existing files, since this might interfere with the scan. If you add additional data (for example, downloading files/content) while scanning, this will prolong the process:

Recuva data recovery tool scan time

Step 2: Recover data.

Once the process is complete, select the folders/files you wish to restore and simply click "Recover". Note that some free space on your storage drive is necessary to restore data:

Recuva data recovery tool recovering data

Create data backups:

Proper file management and creating backups is essential for data security. Therefore, always be very careful and think ahead.

Partition management: We recommend that you store your data in multiple partitions and avoid storing important files within the partition that contains the entire operating system. If you fall into a situation whereby you cannot boot the system and are forced to format the disk on which the operating system is installed (in most cases, this is where malware infections hide), you will lose all data stored within that drive. This is the advantage of having multiple partitions: if you have the entire storage device assigned to a single partition, you will be forced to delete everything, however, creating multiple partitions and allocating the data properly allows you to prevent such problems. You can easily format a single partition without affecting the others - therefore, one will be cleaned and the others will remain untouched, and your data will be saved. Managing partitions is quite simple and you can find all the necessary information on Microsoft's documentation web page.

Data backups: One of the most reliable backup methods is to use an external storage device and keep it unplugged. Copy your data to an external hard drive, flash (thumb) drive, SSD, HDD, or any other storage device, unplug it and store it in a dry place away from the sun and extreme temperatures. This method is, however, quite inefficient, since data backups and updates need to be made regularly. You can also use a cloud service or remote server. Here, an internet connection is required and there is always the chance of a security breach, although it's a really rare occasion.

We recommend using Microsoft OneDrive for backing up your files. OneDrive lets you store your personal files and data in the cloud, sync files across computers and mobile devices, allowing you to access and edit your files from all of your Windows devices. OneDrive lets you save, share and preview files, access download history, move, delete, and rename files, as well as create new folders, and much more.

You can back up your most important folders and files on your PC (your Desktop, Documents, and Pictures folders). Some of OneDrive’s more notable features include file versioning, which keeps older versions of files for up to 30 days. OneDrive features a recycling bin in which all of your deleted files are stored for a limited time. Deleted files are not counted as part of the user’s allocation.

The service is built using HTML5 technologies and allows you to upload files up to 300 MB via drag and drop into the web browser or up to 10 GB via the OneDrive desktop application. With OneDrive, you can download entire folders as a single ZIP file with up to 10,000 files, although it can’t exceed 15 GB per single download.

OneDrive comes with 5 GB of free storage out of the box, with an additional 100 GB, 1 TB, and 6 TB storage options available for a subscription-based fee. You can get one of these storage plans by either purchasing additional storage separately or with Office 365 subscription.

Creating a data backup:

The backup process is the same for all file types and folders. Here’s how you can back up your files using Microsoft OneDrive

Step 1: Choose the files/folders you want to backup.

Click the OneDrive icon in the taskbar

Click the OneDrive cloud icon to open the OneDrive menu. While in this menu, you can customize your file backup settings.

Select Help & Settings and click Settings

Click Help & Settings and then select Settings from the drop-down menu.

Select the Backup tab and click Manage backup

Go to the Backup tab and click Manage backup.

Select folders to backup and click Start backup

In this menu, you can choose to backup the Desktop and all of the files on it, and Documents and Pictures folders, again, with all of the files in them. Click Start backup.

Now, when you add a file or folder in the Desktop and Documents and Pictures folders, they will be automatically backed up on OneDrive.

To add folders and files, not in the locations shown above, you have to add them manually.

Select a file manually and copy it

Open File Explorer and navigate to the location of the folder/file you want to backup. Select the item, right-click it, and click Copy.

Paste the copied file in the OneDrive folder to create a backup

Then, navigate to OneDrive, right-click anywhere in the window and click Paste. Alternatively, you can just drag and drop a file into OneDrive. OneDrive will automatically create a backup of the folder/file.

File statuses in OneDrive folder

All of the files added to the OneDrive folder are backed up in the cloud automatically. The green circle with the checkmark in it indicates that the file is available both locally and on OneDrive and that the file version is the same on both. The blue cloud icon indicates that the file has not been synced and is available only on OneDrive. The sync icon indicates that the file is currently syncing.

Click Help & Settings and click View Online

To access files only located on OneDrive online, go to the Help & Settings drop-down menu and select View online.

Click the Settings cog and click Options

Step 2: Restore corrupted files.

OneDrive makes sure that the files stay in sync, so the version of the file on the computer is the same version on the cloud. However, if ransomware has encrypted your files, you can take advantage of OneDrive’s Version history feature that will allow you to restore the file versions prior to encryption.

Microsoft 365 has a ransomware detection feature that notifies you when your OneDrive files have been attacked and guide you through the process of restoring your files. It must be noted, however, that if you don’t have a paid Microsoft 365 subscription, you only get one detection and file recovery for free.

If your OneDrive files get deleted, corrupted, or infected by malware, you can restore your entire OneDrive to a previous state. Here’s how you can restore your entire OneDrive:


1. If you're signed in with a personal account, click the Settings cog at the top of the page. Then, click Options and select Restore your OneDrive.

If you're signed in with a work or school account,  click the Settings cog at the top of the page. Then, click Restore your OneDrive.

2. On the Restore your OneDrive page, select a date from the drop-down list. Note that if you're restoring your files after automatic ransomware detection, a restore date will be selected for you.

3. After configuring all of the file restoration options, click Restore to undo all the activities you selected.

The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups.

Frequently Asked Questions (FAQ)

How was my computer hacked and how did hackers encrypt my files?

In many instances, victims themselves open ransomware executables since these files are usually disguised as regular content. This malware is primarily distributed through drive-by downloads, spam emails/messages, online scams, malvertising, dubious download sources (e.g., freeware and third-party sites, P2P sharing networks, etc.), illegal program activation ("cracking") tools, and fake updates.

How to open ".rhysida" files?

Encrypted files cannot be opened/used unless they are decrypted.

Where should I look for free decryption tools for Rhysida ransomware?

Some Rhysida's encryptions may be decrypted using a free decryption tool available on the Korean Internet & Security Agency (KISA) website (more information above). Generally, in cases of ransomware attacks, we recommend checking out the No More Ransom project website (more information above).

I can pay you a lot of money, can you decrypt files for me?

We do not offer such services. In fact, aside from cases involving deeply flawed ransomware, decryption is impossible without the attackers' interference. Therefore, third-parties offering paid decryption are often scams or middleman services between victims and criminals.

Will Combo Cleaner help me remove Rhysida ransomware?

Yes, Combo Cleaner will scan your computer and eliminate detected ransomware infections. It must be mentioned that while using an anti-virus program is the first step in ransomware recovery – security software cannot restore encrypted files.

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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.

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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.

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