Mr.Dec Ransomware

Also Known As: Mr.Dec virus
Distribution: Low
Damage level: Severe

Mr.Dec ransomware removal instructions

What is Mr.Dec?

Mr.Dec is a ransomware-type virus discovered by Michael Gillespie. This malware is designed to encrypt most stored files and add the "[ID]victim's_ID[ID]" appendix to each filename. For example, "sample.jpg" might be renamed to a filename such as "sample.jpg[ID]gh839ag14hiol4ag[ID]". Compromised data immediately becomes unusable. Furthermore, after successful encryption, Mr.Dec generates an HTML application ("Decoding help.hta") and places copy in every existing folder.

The HTML application contains a short message informing users of the encryption and encouraging them to immediately contact Mr.Dec's developers via one of the email addresses provided. Victims are then supposedly provided with further decryption instructions. Unfortunately, no additional information is provided and, thus, it is currently unknown which cryptography (symmetric or asymmetric) Mr.Dec employs. Nevertheless, a unique decryption key (generated individually for each victim) is necessary to restore data. Unfortunately, Mr.Dec's developers store all keys on a remote server and victims are encouraged to pay a ransom for their release. The cost is currently unknown - as mentioned before, all details are provided via an email. Note that ransoms typically fluctuate between $500 and $1500 to be paid in a type of cryptocurrency (Bitcoins, Monero or another). The HTML app also states that victims have just three days to submit payments (it contains a countdown timer), otherwise decryption keys are permanently deleted and restoring files becomes impossible. Despite these threats and demands, cyber criminals should never be trusted - no matter what the cost, do not pay. These people ignore victims once payments are submitted. Paying typically gives no positive result and users are scammed. Therefore, we strongly advise you to ignore all requests to contact these people or especially to submit payments. There are currently no tools capable of decrypting data compromised by Mr.Dec free of charge. There is only one solution: to restore everything from a backup.

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

Mr.Dec decrypt instructions

There are many ransomware-type viruses virtually identical to Mr.Dec including Sigrun, Everbe, and Horsuke - these are just some examples from many. Although these viruses are developed by different cyber criminals, all have identical behavior - they encrypt stored files and blackmail victims. These viruses typically have just two major differences: 1) size of ransom, and; 2) type of cryptography used. Unfortunately, most use algorithms (e.g., RSA, AES, etc.) that generate unique decryption keys. Therefore, unless the virus is not fully developed or has certain bugs/flaws, file decryption manually without involvement of developers (contacting these people is not recommended) is impossible. Viruses such as Mr.Dec are one of the main reasons why you should keep regular data backups, however, remember to store them on an unplugged storage device (e.g., Flash drive, external hard drive or similar) or a remote server (such as Cloud). If not, backups are encrypted with regular files.

How did ransomware infect my computer?

Developers proliferate ransomware in various ways, however, the most popular four are: 1) spam emails [malicious attachments]; 2) third party software download sources [peer-to-peer {P2P} networks, freeware download websites, free file hosting websites, etc.]; 3) fake software update tools, and; 4) trojans. Spam emails are delivered with malicious attachments (e.g., JavaScript files, MS Office documents and similar) that, once opened, execute scripts designed to download and install malware. Unofficial download sources present malicious executables as legitimate software, thereby tricking users into downloading and installing viruses. Fake updaters infect the system by exploiting outdated software bugs/flaws or simply downloading and installing malware rather than updates. Trojans open "backdoors" for other viruses to infiltrate the system. Ultimately, the main reasons for computer infections are poor knowledge and careless behavior.

Threat Summary:
NameMr.Dec virus
Threat TypeRansomware, Crypto Virus, Files locker
SymptomsCan'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.
Distribution methodsInfected email attachments (macros), torrent websites, malicious ads.
DamageAll 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 Mr.Dec 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?

To prevent ransomware infections, be very cautious when browsing the Internet. Think twice before opening email attachments. If the files seem irrelevant or have been received from a suspicious/unrecognizable email address, delete the email immediately and certainly do not open any attachments. Furthermore, download your software from official sources only (via direct download links), rather than using third party downloaders/installers. These tools are monetized by promoting (including) rogue programs, and thus should never be used. The same applies to updating software - keep installed apps up-to-date using implemented functions or tools provided by official developers only. Having a reputable anti-virus/anti-virus suite installed and running is also paramount. The key to computer safety is caution.

Text presented in Mr.Dec ransomware HTML application ("Decoding help.hta"):

You are unlucky! The terrible virus has captured your files! For decoding please contact by email or


1. In the subject line, write your ID.
2. Attach 1-2 infected files that do not contain important information (less than 2 mb)
3. Attach the file with the location c:\Windows\DECODE KEY.KEY
are required to generate the decoder and restore the test file.
Hurry up! Time is limited!
At the end of this time, the private key for generating the decoder will be destroyed. Files will not be restored!

Screenshot of files encrypted by Mr.Dec ("[ID]victim's_ID[ID]" extension):

Files encrypted by Mr.Dec

Mr.Dec ransomware removal:

Instant automatic removal of Mr.Dec 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 Mr.Dec 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 Mr.Dec 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 Mr.Dec 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 Mr.Dec 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 Mr.Dec 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 Mr.Dec, 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 Mr.Dec 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 Mr.Dec ransomware: