Nemucod ransomware - How to remove

Nemucod ransomware, also referred to as Nemucod.CRYPTED, Decrypt.txt ransomware or JS-Nemucod, is a new ransomware trojan. It is one element of bilateral Nemucod TrojanDownloader. The other element is malware named Kovter (Poweliks) which is installed along with Nemucod. Another interesting point worth mentioning, is that this file encryptor breaks the encryption process into two steps. The files it downloads do not start encryption right away. They are launched after the execution of Command Prompt which finds the files for encryption. For further information about Nemucod ransoware read the following paragraph.

About Nemucod Ransomware

Nemucod ransomware is written in Javascript and uses asymmetric AES-256/RSA-2048 algorithm. It downloads and stores an executable 5021052.exe to %TEMP% folder. Then, Javascript installers create command and batch files which will execute commands on Windows command-line interpreter that, in turn, will scan for data to be encrypted. Data corrupted ranges from documents to music and video files, etc. .CRYPTED extension is appended to the targeted files. This suggests that Nemucod ransomware is a version of TrueCrypt ransomware. Albeit, it can add .CCC or .NEMUCOD extension. After the data has been chosen, 5021052.exe is started with the command and batch files as arguments. This executable encrypts the first 2048 bytes of the files with XOR cipher. When data is encrypted, CMD script adds registry entries to Windows Startup to make Nemucod ransomware start automatically every time Windows is launched.

After all this is accomplished, batch script erases itself from Command Prompt. The ransom note is displayed in Decrypted.txt file. Currently it ranges from around 0.4 to 0.52985 BTC, that is 179.61 to 237.92 USD. It has been noticed that this ransomware connects to various servers: ujjwaljeweller.com, topikriau.com, yc4tuna.com, yingyigood.com, xn--oi2bq3ygphw3bbzh.com. And it is said that Nemucod ransomware spreads Teslacrypt ransomware.

How does Nemucod Ransomware Infect Computer?

Nemucod trojan is spread through spam e-mail attachments. These attachments contain .js (JavaScript) files which are infected with this ransomware. They tend to be disguised as official letters from legitimate companies and organizations. These fake e-mails may even have logotypes, etc. The other method of Nemucod ransomware distribution is exploits aiming at system vulnerabilities such as outdated and insecure software, etc.

How to Decrypt Files Encrypted by Nemucod Ransomware?

A security expert Fabian Wosar of Emisoft has developed decryption tools for Windows of Nemucod ransomware. They are offered free at decrypter.emisoft.com. Go to the following address and download decrypt_nemucod.exe. Save the file on your desktop. In order the decryption key be recognized, you have to drag both files – the encrypted and the unencrypted – simultaneously onto the decryptor icon (if you do not have the intact file remained, use the picture of C:\Users\Public folder). User Account Control (UAC) prompt will be displayed. Click YES button. When the decryption key is recognized, it will present you with the window, ‘‘Decryption key found’’. This key should fit to restore all corrupted data. Click OK button. Then, the License Agreement ensues. Again, click OK. Now you are shown the main Decryptor window. If there are data encrypted apart from the disk C, click ADD FILE(S) button to add another drive. Then, click DECRYPT. When the decryption is over, you will be presented with the window of the results. All files by now should be decrypted. For Kovter removal use this link http://www.bleepingcomputer.com/virus-removal/remove-kovter-trojan.

To remove Nemucod ransomware, employ credible malware removal tools such as Spyhunter, Malwarebytes. These utilities will scan your computer for any extra malware infections.

Update of the 12th of December, 2016. The most recent decryptor for Nemucod has been released.

How to recover Nemucod ransomware encrypted files and remove the virus

Step 1. Restore system into last known good state using system restore

1. Reboot your computer to Safe Mode with Command Prompt:

for Windows 7 / Vista/ XP

• Start → Shutdown → Restart → OK.
• Press F8 key repeatedly until Advanced Boot Options window appears.
• Choose Safe Mode with Command Prompt.

for Windows 8 / 10

• Press Power at Windows login screen. Then press and hold Shift key and click Restart.
• Choose Troubleshoot → Advanced Options → Startup Settings and click Restart.
• When it loads, select Enable Safe Mode with Command Prompt from the list of Startup Settings.

 

2.Restore System files and settings.

• When Command Prompt mode loads, enter cd restore and press Enter.
• Then enter rstrui.exe and press Enter again.
• Click “Next” in the windows that appeared.
• Select one of the Restore Points that are available before Nemucod ransomware has infiltrated to your system and then click “Next”.
• To start System restore click “Yes”.

 

Step 2. Complete removal of Nemucod ransomware

After restoring your system, it is recommended to scan your computer with an anti-malware program, like Spyhunter and remove all malicious files related to Nemucod ransomware. You can check other tools here.  

Step 3. Restore Nemucod ransomware affected files using Shadow Volume Copies

If you do not use System Restore option on your operating system, there is a chance to use shadow copy snapshots. They store copies of your files that point of time when the system restore snapshot was created. Usually Nemucod ransomware tries to delete all possible Shadow Volume Copies, so this methods may not work on all computers. However, it may fail to do so. Shadow Volume Copies are only available with Windows XP Service Pack 2, Windows Vista, Windows 7, and Windows 8. There are two ways to retrieve your files via Shadow Volume Copy. You can do it using native Windows Previous Versions or via Shadow Explorer. a) Native Windows Previous Versions Right-click on an encrypted file and select Properties → Previous versions tab. Now you will see all available copies of that particular file and the time when it was stored in a Shadow Volume Copy. Choose the version of the file you want to retrieve and click Copy if you want to save it to some directory of your own, or Restore if you want to replace existing, encrypted file. If you want to see the content of file first, just click Open.

b) Shadow Explorer It is a program that can be found online for free. You can download either a full or a portable version of Shadow Explorer. Open the program. On the left top corner select the drive where the file you are looking for is a stored. You will see all folders on that drive. To retrieve a whole folder, right-click on it and select “Export”. Then choose where you want it to be stored.

Step 4. Use Data Recovery programs to recover Nemucod ransomware encrypted files

There are several data recovery programs that might recover encrypted files as well. This does not work in all cases but you can try this:

• We suggest using another PC and connect the infected hard drive as slave. It is still possible to do this on infected PC though.
• Download a data recovery program.
• Install and scan for recently deleted files.

Note: In many cases it is impossible to restore data files affected by modern ransomware. Thus I recommend using decent cloud backup software as precaution. We recommend checking out Carbonite, BackBlaze, CrashPlan or Mozy Home.

Manual removal