Nasoh ransomware removal guide

Also Known As: Nasoh virus
Distribution: Low
Damage level: Severe

Nasoh ransomware removal instructions

What is Nasoh?

First discovered by Michael Gillespie, Nasoh is one of many ransomware-type infections from the Djvu family. The purpose of this virus is to stealthily infiltrate computers and encrypt data so that developers can make ransom demands by offering paid recovery of files. This ransomware is also designed to append each filename with the ".nasoh" extension (e.g., "sample.jpg" -> "sample.jpg.nasoh"). A text file named "_readme.txt" is also created, copies of which are stored in most existing folders. This text file contains a ransom-demand message.

Most ransomware infections (including Nasoh) from the Djvu family deliver an identical ransom-demand message. The message claims that files are compromised (encrypted) and that victims must purchase a decryption key to restore them. Unfortunately, decryption requires a key. Nasoh compromises data using a cryptography algorithm that generates a unique decryption key for each victim. Furthermore, victims cannot access their keys, since they are stored on a server owned by Nasoh's developers. This enables criminals to blackmail the victims. The cost of each key is equivalent to $980, however, victims are offered a 50% discount if they contact developers within 72 hours of encryption. These people also offer free decryption of one file as 'proof' that they are capable of restoring data. In any case, never trust these people. Malware developers often ignore victims after payments are submitted. Therefore, paying often gives no positive result and users are scammed. You are strongly advised to ignore all ransom-demand messages - never send money and do not attempt to contact them. Note that this ransomware checks whether the system has an internet connection and if the server is responding. If not, it encrypts data with a hard-coded "offline key", which is used for multiple encryptions. Therefore, try restoring data with a tool developed by Michael Gillespie. If that does not work, the only possible solution is to restore everything from a backup.

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

Nasoh decrypt instructions

Nasoh is virtually identical to dozens of other ransomware-type infections such as Yoba, BORISHORSE, 2k19cry, etc. Although the developers are different, all of these infections have virtually identical behavior - they compromise files (usually, by encryption) and make ransom demands. There are typically just two major differences: 1) size of ransom, and; 2) type of encryption algorithm used. Encryptions are performed using cryptographies such as RSA, AES, and similar, that generate unique decryption keys. Therefore, unless the ransomware has bugs or flaws, it is impossible to restore without developers' involvement. Infections such as Nasoh are one of the main reasons why you should maintain regular backups. Bear in mind, however, that locally stored backups are compromised together with regular data. Therefore, store backups on a remote server (e.g., Cloud) or unplugged storage device (external hard drive, Flash drive, or similar). Also have multiple backup copies stored in different locations to prevent losses caused by damaged servers/hardware.

How did ransomware infect my computer?

To proliferate ransomware-type infections, developers often employ spam email campaigns, third party software download sources (Peer-to-Peer [P2P] networks, free file hosting websites, freeware download websites, etc.), trojans, and fake software 'cracks' and updaters. Criminals use spam campaigns to send hundreds of thousands of deceptive emails which contain deceptive messages encouraging recipients to open attached malicious links/files. To give the impression of legitimacy and increase the chance of tricking recipients, criminals present malicious attachments as various important documents, such as bills, invoices, receipts, and so on. Unofficial download sources are also used in a similar manner. Criminals present malicious executables as legitimate software, thereby tricking users into manual download/installation of malware. Trojans are essentially malicious lightweight applications designed to infiltrate computers and stealthily download/install additional malware. Fake cracking/update tools infect systems rather than activating/updating software. In summary, poor knowledge of these threats and careless behavior are the main reasons for computer infections.

Threat Summary:
Name Nasoh virus
Threat Type Ransomware, Crypto Virus, Files locker
Detection Names Avast (Win32:Trojan-gen), BitDefender (Trojan.GenericKD.32253579), ESET-NOD32 (Win32/Filecoder.STOP.A), Kaspersky (Trojan.Win32.Zenpak.hwl), Full List Of Detections (VirusTotal)
Encrypted Files Extension .nasoh
Ransom Demanding Message _readme.txt
Ransom Amount $980/$490
Cyber Criminal Contact,
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 fake a Windows Update window, modify the 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, unofficial activation and updating tools.
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 Nasoh virus our malware researchers recommend scanning your computer with Spyhunter.
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Free scanner checks if your computer is infected. To remove malware, you have to purchase the full version of Spyhunter.

How to protect yourself from ransomware infections?

The key to computer safety is caution. Therefore, pay close attention when browsing the internet and downloading/installing/updating software. Be cautious when handling email attachments. If the received file/link is irrelevant or the sender's email address seems suspicious/unrecognizable, do not open anything and delete the email immediately. Download apps from official sources only and, if possible, using direct download links. Third party downloaders/installers often include rogue applications - using them is risky. The same applies to software updates. Employ only implemented functions or tools provided by the official developer. Software piracy is a cyber crime and cracking installed applications is illegal. In addition, the risk of infection is extremely high, since many of these tools are fake. Therefore, using cracking tools should never be considered. Have a reputable anti-virus/anti-spyware suite installed and running - this will detect and eliminate infections before they do any harm. If your computer is already infected with Nasoh, we recommend running a scan with Spyhunter for Windows to automatically eliminate this ransomware.

Text presented in Nasoh ransomware 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:

Your personal ID:

Screenshot of files encrypted by Nasoh (".nasoh" extension):

Files encrypted by Nasoh

Malware researcher Michael Gillespie has developed a decryption tool that might restore your data if it was encrypted using an "offline key". As mentioned, each victim gets a unique decryption key, all of which are stored on remote servers controlled by cyber criminals. These are categorized as "online keys", however, there are cases whereby the infected machine has no Internet connection or the server is timing out/not responding. If this is the case, Nasoh will use an "offline encryption key", which is hard-coded. Cyber criminals change offline keys periodically 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 proportion of "offline keys" have so far been gathered. You can download the decrypter by clicking this link (note that the download link remains identical, even though the decrypter is being continually updated). Your files will be restored only if the list of gathered keys includes 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 ransomware from the Djvu family, Nasoh also displays a fake Windows update pop-up during the encryption:

Djvu ransomware family fake update

IMPORTANT NOTE! - As well as encrypting data, ransomware-type infections from the Djvu malware family also install 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 done to prevent users from accessing malware security websites and seeking 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

Nasoh ransomware removal:

Instant automatic removal of Nasoh 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 Nasoh 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 Nasoh 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 Nasoh 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 Nasoh 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 Nasoh 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 Nasoh, 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 Nasoh ransomware.

Note that Windows 10 Fall Creators Update includes a "Controlled Folder Access" feature that blocks ransomware attempts to encrypt your files. By default, this feature automatically protects files stored in the Documents, Pictures, Videos, Music, Favorites as well as Desktop folders.

Controll Folder Access

Windows 10 users should install this update to protect their data from ransomware attacks. Here is more information on how to get this update and add an additional protection layer from ransomware infections.

HitmanPro.Alert CryptoGuard - detects encryption of files and neutralises any attempts without need for user-intervention:

hitmanproalert ransomware prevention application

Malwarebytes Anti-Ransomware Beta uses advanced proactive technology that monitors ransomware activity and terminates it immediately - before reaching users' files:

malwarebytes anti-ransomware

  • The best way to avoid damage from ransomware infections is to maintain regular up-to-date backups. More information on online backup solutions and data recovery software Here.

Other tools known to remove Nasoh 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.

QR Code
Nasoh virus QR code
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