Removal of Gerosan ransomware infection

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

Gerosan ransomware removal instructions

What is Gerosan?

Gerosan is categorized as ransomware, malicious software that is designed to prevent victims from accessing operating system/data until a ransom is paid. In other words, it encrypts files with a strong cryptography algorithm. Gerosan changes filenames of encrypted files by adding the ".gerosan" extension. For example, it renames a file named "1.jpg" to "1.jpg.gerosan" and so on. Like most ransomware-type programs, it creates a ransom note, in this case a text file named "_readme.txt". This note can be found in folders that contain encrypted data. Gerosan belongs to Djvu ransomware family and the person who discovered this malware is Michael Gillespie.

As mentioned in the text file (ransom note), this ransomware encrypts all data, such as photos, documents, databases and so on. The only way to decrypt it is to purchase a decryption tool and a unique key. Their price is $980, however, victims who will contact Gerosan's developers in 72 hours after encryption will get a 50% discount. These cyber criminals can be contacted via email ( or or Telegram (@datarestore). Before making a payment victims can send them one file that they will decrypt for free. They offer it to prove that they have the decryption tool/key. However, we do not recommend to pay them. In fact, we advise not to trust any ransomware developers. Typically, they do not send their victims decryption tools and/or keys even if a ransom is paid. If there was no Internet connection or remote server used by cyber criminals was not responding while Gerosan was encrypting files, then it might be possible to decrypt them with an offline decryption tool. However, if that is not the case, then the only way to restore files for free is to do it using data backup. As a rule, ransomware-type programs cause encryptions that are impossible to 'crack'. In other words, the only way to decrypt data encrypted with ransomware is to use the right decryption tool or/and key. Unfortunately, these tools can be provided only by people/cyber criminals who developed the ransomware.

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

Gerosan decrypt instructions

There are numerous similar ransomware-type programs, other examples are Myskle, Boston and Kjh. In most cases these programs have two main things in common: they encrypt/lock victim's files and their encryptions cannot be decrypted without the right decryption tools/keys. The main differences are the size of a ransom and cryptography algorithm (symmetric or asymmetric) that ransomware uses to encrypt data. Unfortunately, decryptions without interference or cyber criminals (people who developed ransomware) are possible only if the program is not finished. In other words, it has bugs, flaws and so on. That is the main reason why it is important to always have a data backup created. Besides, it should be kept on some remote server (like Cloud) or unplugged/disconnected storage device.

How did ransomware infect my computer?

In most cases cyber criminals spread malware through other programs of this kind called trojans, spam campaigns, fake software updaters, software 'cracking' tools and questionable software download sources. Trojan is a type of malware that often is used to cause chain infections. Simply said, if a trojan is installed on a system, then it spreads other malicious programs, including ransomware. To proliferate malware through spam campaigns, cyber criminals send emails that include malicious attachments. Operating systems get infected when people open them. Typically, attached files are Microsoft Office documents, archive files (i.e., ZIP, RAR), executables (.exe and other files), PDF documents, JavaScript files so on. Fake software updating tools infect systems by exploiting bugs, flaws of installed and outdated software or/and by downloading and installing malware instead of updating, fixing software. Software 'cracking' tools infect systems in a similar way: these tools supposed to bypass paid activations, however, they often download and install malware instead. Untrustworthy, unofficial websites, free file hosting, freeware download websites, third party downloaders, Peer-to-Peer networks and other similar software download channels can be used to proliferate malicious programs too. Cyber criminals present uploaded malware as legitimate files. When people download and open them, they install malware.

Threat Summary:
Name Gerosan virus
Threat Type Ransomware, Crypto Virus, Files locker
Encrypted Files Extension .gerosan
Ransom Demanding Message _readme.txt
Ransom Amount $980/$480
Cyber Criminal Contact,, @datarestore (Telegram)
Symptoms Can't open files stored on your computer, previously functional files now have a different extension, for example my.docx.locked. A ransom demanding message is displayed on your desktop. Cyber criminals are asking to pay a ransom (usually in bitcoins) to unlock your files.
Additional Information This malware is designed to show fake Windows Update window, modify Windows "hosts" file (to prevent users from accessing cyber security websites) and inject AZORult trojan into the system.
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.

To eliminate Gerosan virus our malware researchers recommend scanning your computer with Spyhunter.
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How to protect yourself from ransomware infections?

We do not recommend to open attachments (or links) that are included in irrelevant emails, especially if they are received from unknown or suspicious addresses. Update software with implemented tools or functions that are provided by official developers. Download files or software from official, trustworthy websites. Do not use any of the aforementioned tools for that. If installed software is not free, it should not be activated using unofficial, third party tools. These tools are illegal and often infect systems with malicious programs. Additionally, have a reputable anti-virus or anti-spyware program installed, do not disable it without a good reason and scan the system for viruses regularly. If your computer is already infected with Gerosan, we recommend running a scan with Spyhunter for Windows to automatically eliminate this ransomware.

Text presented in Gerosan ransomware's text file ("_readme.txt"):

Don't worry, you can return all your files!
All your files like photos, 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:
Our Telegram account:
Your personal ID:

Screenshot of files encrypted by Gerosan (".gerosan" extension):

Files encrypted by Gerosan

Malware researcher Michael Gillespie has developed a decryption tool that might restore your data if it was encrypted using an "offline key". As we've already mentioned, each victim gets a unique decryption key and all of them are stored in remote servers controlled by cyber criminals. These are categorized as "online keys". However, there are cases when the infected machine has no Internet connection or the server is timing out/not responding. If that is the case, Gerosan will use an "offline encryption key", which is hard-coded. Now it is worth mentioning that cyber criminals change offline keys every now and again. This is being done to prevent multiple encryptions with the same key. Meanwhile, Michael Gillespie continually gathers offline keys and updates the decrypter. However, the chances of successful decryption are still very low, since only a very small portion of "offline keys" has been gathered. You can download the decrypter by clicking this link (note that the download link remains the same, despite the fact that decrypter is being continually updated). Your files will be restored only if the list of gathered keys will include the one that was used to encrypt your data.

Screenshot of STOP/Djvu decrypter by Michael Gillespie:

STOP/Djvu ransomware decrypter by Michael Gillespie

As with most of ransomware from Djvu family, Gerosan also displays a fake Windows update pop-up during the encryption:

Djvu ransomware family fake update

IMPORTANT NOTE! - Aside from encrypting data, ransomware-type infections from Djvu malware family also installs a trojan-type virus called AZORult, which is designed to steal various account credentials. Moreover, this malware family is designed to 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 carried out with the intention of making users unable to access malware security websites and seek help. Our website ( 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:

Tro Ransomware adding websites to Windows Hosts file

Gerosan ransomware removal:

Instant automatic removal of Gerosan virus: Manual threat removal might be a lengthy and complicated process that requires advanced computer skills. Spyhunter is a professional automatic malware removal tool that is recommended to get rid of Gerosan virus. Download it by clicking the button below:
▼ DOWNLOAD Spyhunter By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. Free scanner checks if your computer is infected. To remove malware, you have to purchase the full version of Spyhunter.

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 Gerosan 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 Gerosan 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 Gerosan 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 Gerosan 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 Gerosan, 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 Gerosan ransomware.

Note that Windows 10 Fall Creators Update includes "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default this feature automatically protects files stored in 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's more information on how to get this update and add 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 Gerosan ransomware:

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

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.

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Malware activity

Global virus and spyware activity level today:

Medium threat activity

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

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Gerosan virus QR code
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