What is Gujd ransomware?
Gujd is part of the Djvu ransomware family. It encrypts files and appends the ".gujd" extension to their filenames. For example, Gujd renames a file named "1.jpg" to "1.jpg.gujd", "2.jpg" to "2.jpg.gujd", and so on. To provide instructions on how to contact the attackers (and other details), Gujd creates a ransom note (the "_readme.txt" file).
Gujd ransomware in detail
Most ransomware variants generate a ransom note containing contact and payment information like an email address, price of a decryption tool, cryptocurrency wallet address, etc. Gujd's ransom note contains two email addresses and two prices, and encourages to contact cybercriminals within 72 hours after the attack.
More precisely, "_readme.txt" file informs victims that all their files (photos, documents, databases, etc.) are encrypted. To recover files, victims have to use a decryption program and a unique key that can be purchased for $980 or $490 (it depends on how fast victims will contact the attackers).
Cybercriminals can be contacted via email@example.com or firstname.lastname@example.org email address. An email can have one file attached to it. To prove that the attackers have decryption tools, they offer to decrypt that attached file for free (the attached file cannot contain valuable information).
As a rule, ransomware victims have two options: to decrypt files with a tool purchased from cybercriminals or restore files from a data backup. It is strongly recommended not to pay ransom - it is common that victims do not receive any decryption tool even after the payment (they get scammed).
Usually, cybercriminals behind ransomware attacks are the only ones who can help victims to recover files (have the right decryption tools). In other words, it is rarely possible to decrypt files encrypted by ransomware-type malware without paying a ransom because there are no free decryption tools available on the Internet.
One more important detail about the malware of this type is that it could cause further encryptions (encrypt more files) or infect other computers on the same network. It can be prevented by uninstalling ransomware from the operating system. It is worth mentioning that encrypted files remain inaccessible even after the uninstallation of ransomware.
Screenshot of a message encouraging users to pay a ransom to decrypt their compromised data:
Similarities with other ransomware variants
A couple of examples of other ransomware variants are LOWPRICE, Lockhyp, and Wwka. As a rule, most of them are more or less similar: they are designed to encrypt files and generate a ransom note (provide instructions on how to pay for data decryption, contact the attackers, and other information regarding data recovery).
The major differences between ransomware variants are the prices of the decryption tools and cryptographic algorithms (symmetric or asymmetric) that they use to block victims from accessing their files. Most of the times, cybercriminals behind ransomware are the only ones who have the right decryption tool (or tools).
Most ransomware victims cannot decrypt files without tools purchased from the attackers unless ransomware has some bugs, flaws or there is a free decryption tool available on the Internet. Therefore, it is recommended to have data backed up and keep it stored on some remote server like Cloud, or an unplugged storage device.
How did ransomware infect my computer?
Another popular way to distribute malware is to trick users into installing certain trojans on their computers. There is a type of trojans that can install additional malware (infect computers with additional malware). In most cases, those trojans are distributed using one of the ways describes in this section. It is worth mentioning that trojans usually are designed to look like legitimate programs.
Another popular way to trick users into installing malware is through unofficial websites, freeware download websites, free file hosting pages, Peer-to-Peer networks (e.g., torrent clients, eMule and), third-party downloaders, and other unreliable sources for downloading files, programs. In such cases, users install malware by opening downloaded malicious files.
A couple of other popular channels to distribute malicious programs are fake software updaters and software cracking tools. Fake updaters look like official tools that are supposed to install updates, fixes. However, they install unwanted, malicious software, or infect systems by exploiting bugs, flaws of outdated software.
Software cracking tools are illegal programs that are supposed to bypass the activation of licensed software. However, it is common for these tools (and installers for cracked software) to have malware hidden in them. Cybercriminals behind cracking tools target individuals who seek to avoid paying for licensed software.
|Threat Type||Ransomware, Crypto Virus, Files locker|
|Encrypted Files Extension||.gujd|
|Ransom Demanding Message||_readme.txt|
|Cyber Criminal Contactemail@example.com, firstname.lastname@example.org|
|Detection Names||Avast (Win32:PWSX-gen [Trj]), AVG (Win32:PWSX-gen [Trj]), Fortinet (W32/GenKryptik.ERHN!tr), Kaspersky (UDS:Exploit.Win32.Shellcode.gen), Microsoft (Trojan:Win32/Sabsik.FL.A!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.|
|Additional Information||This malware is designed to show a fake Windows Update window and modify the Windows "hosts" file to prevent users from accessing cyber security websites (more information below).|
|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.
How to protect yourself from ransomware infections?
Installed programs have to be updated or activated with tools or functions that their official developers provide. Third-party tools usually are malicious. Also, the use or distribution of cracked or pirated software is illegal. Files attached to irrelevant emails that are received from unknown, suspicious addresses should not be opened.
Website links in emails of this kind should not be opened too. Cybercriminals often disguise their emails as official, important, letters from legitimate companies, etc., and use links or attachments in their emails to distribute malicious software. Programs (and files) should be downloaded from official, trustworthy websites.
It is not safe to use other channels and sources (like unofficial pages, third-party downloaders). Virus scans should be performed regularly, and it should be achieved using a reputable antivirus or anti-spyware software. If your computer is already infected with Gujd, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate this ransomware.
Text presented in Gujd ransomware's text file :
Don't worry, you can return all your files!
All your files like pictures, databases, documents and other important are encrypted with strongest encryption and unique key.
The only method of recovering files is to purchase decrypt tool and unique key for you.
This software will decrypt all your encrypted files.
What guarantees you have?
You can send one of your encrypted file from your PC and we decrypt it for free.
But we can decrypt only 1 file for free. File must not contain valuable information.
You can get and look video overview decrypt tool:
Price of private key and decrypt software is $980.
Discount 50% available if you contact us first 72 hours, that's price for you is $490.
Please note that you'll never restore your data without payment.
Check your e-mail "Spam" or "Junk" folder if you don't get answer more than 6 hours.
To get this software you need write on our e-mail:
Reserve e-mail address to contact us:
Your personal ID:
Screenshot of files encrypted by Gujd (".gujd" extension):
Screenshot of fake Windows update pop-up displayed during the encryption:
IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also add a number of entries to the Windows "hosts" file. The entries contain URLs of various websites, most of which are related to malware removal. This is done to prevent users from accessing malware security websites and seeking help. Our website (PCrisk.com) is also on the list.
Removing these entries, however, is simple - you can find detailed instructions in this article (note that, although the steps are shown in the Windows 10 environment, the process is virtually identical on all versions of the Microsoft Windows operating system).
Screenshot of websites added to Windows hosts file:
There are currently two versions of Djvu ransomware infections: old and new. The old versions were designed to encrypt data by using a hard-coded "offline key" whenever the infected machine had no internet connection or the server was timing out/not responding.
Therefore, some victims were able to decrypt data using a tool developed by cyber security researcher, Michael Gillespie, however, since the encryption mechanism has been slightly changed (hence the new version, released in August, 2019), the decrypter no longer works and it is not supported anymore.
If your data has been encrypted by an older version, you might be able to restore it with the another tool developed by Emsisoft and Michael Gillespie. It supports a total of 148 Djvu's variants and you can find more information, as well as download link and decryption instructions in Emsisoft's official page.
Screenshot of Djvu decryption tool by Emsisoft and Michael Gillespie:
Additionally, Emsisoft is now providing a service that allows to decrypt data (again, only if it was encrypted by Djvu variants released before August, 2019) for those victims who have a pair of the same file before and after the encryption. All victims have to do is upload a pair of original and encrypted file to Emsisoft's Djvu decryption page and download the aforementioned decryption tool (the download link will be provided after uploading files).
Note that the file processing may take some time so be patient. It is also worth mentioning that the system must have an Internet connection during the entire decryption process, otherwise it will fail.
Screenshot of Emsisoft's Djvu decryption service page:
Some victims state that they've successfully restored a part of encrypted data using PhotoRec tool developed by CGSecurity (Christophe Grenier). You can download this tool from CGSecurity's official website.
Screenshot of PhotoRec application:
Now it is worth noting that Djvu ransomware does not encrypt the entire file. Instead, it encrypts only a portion (start) of the file, thereby making it unusable. Luckily, in some cases it is possible to restore other part of the file, which is not encrypted. This is useful when it comes to audio/video files, because even though the start won't be restored, you'll still be able to use most of it.
To restore audio/video data we advise you to use Media_Repair tool developed by DiskTuna. This tool is extremely simple and completely free. You can find the user manual as well as download the tool directly from DiskTuna's website.
Screenshot of Media_Repair application developed by DiskTuna:
Gujd ransomware removal:
Instant automatic malware removal:
Manual threat removal might be a lengthy and complicated process that requires advanced computer 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:
Video suggesting what steps should be taken in case of a ransomware infection:
- What is Gujd virus?
- STEP 1. Reporting ransomware to authorities.
- STEP 2. Isolating the infected device.
- STEP 3. Identifying the ransomware infection.
- STEP 4. Searching for ransomware decryption tools.
- STEP 5. Restoring files with data recovery tools.
- STEP 6. Creating data backups.
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):
- USA - Internet Crime Complaint Centre IC3
- United Kingdom - Action Fraud
- Spain - Policía Nacional
- France - Ministère de l'Intérieur
- Germany - Polizei
- Italy - Polizia di Stato
- The Netherlands - Politie
- Poland - Policja
- Portugal - Polícia Judiciária
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:
Click the "Change adapter settings" option in the upper-left corner of the window:
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".
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":
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).
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).
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).
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):
Example 2 (.iso [Phobos] ransomware):
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.
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.
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:
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:
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 cloud icon to open the OneDrive menu. While in this menu, you can customize your file backup settings.
Click Help & Settings and then select Settings from the drop-down menu.
Go to the Backup tab and click Manage 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.
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.
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.
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.
To access files only located on OneDrive online, go to the Help & Settings drop-down menu and select View online.
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.