Nobu ransomware is a file-coder virus that is part of STOP/DJVU malware family. It can access the computer via various penetration methods especially through the spam email campaign. Once Nobu enters the computer, it is able to lock the files using high level of encryption that is quite impossible to decipher without the corresponding decryption software. Then, Nobu ransomware releases a payment request via its ransom note file generated on the same folder as the encrypted data.
How Nobu Virus Infects the Computer?
This ransomware is part of the notorious family of malware STOP/DJVU. Like older variants as Weui, Sglh, and Lisp that uses different scheming ways to enter the computer, there is no other way for Nobu to spread but to adopt the same techniques.
Nobu ransomware is seen to be deployed quickly and easily via mass-mailing campaign. This is a technique where the virus is carried out on the email message as an attachment. By masquerading as official document file from a reputable organization or business entity, it can easily persuade the recipients to open the attached file. In this case, Nobu ransomware initializes the computer infection and launch a file coding operation.
Next to spam emails, cracked software or any kind of malicious file installers are observed as another co-conspirator to widely spread Nobu ransomware. Programs that computer users may download intentionally from file-sharing sites, software piracy platforms, or freeware sites could contain the malicious code that may lead to Nobu ransomware infection. Therefore, avoid the mentioned sites and any obtainable apps they are offering.
Nobu File Encryption / Decryption
When Nobu ransomware infects the computer, it will drop several files on the System folder. The virus also creates an auto-start technique to run the malicious code during Windows boot-up. Next, it will communicate to remote server to accept commands. A public key is also requested from the server that Nobu will use during file-decryption.
The focal point of the attack is file encryption where the virus is using a complex method to make the important user’s files inaccessible. Apart from encryption techniques, data are also appended with .nobu file extension. As a result, the ordinary file image.jpg will turn into image.jpg.nobu after the encryption process.
As what goes with the entire ransomware attack, the hackers will demand ransom payment from victims if they want to recovery the encrypted data. In this particular case, people who created Nobu ransomware are demanding $980. This price and the discounted value are clearly stipulated in the ransom note file. Please see screenshot image of the ransom note below.
|Threat Name||Nobu Ransomware, STOP, DJVU|
|Threat Type||Crypto-virus, File Locker, Encryption Virus|
|Encryption Method||AES-256 combined with RSA-1024 Asymmetric Encryption|
|Ransom Amount||$980 (worth of Bitcoin)|
|Ransomware Note File||_readme.txt|
|Virus Alias||AVG : Win32:DropperX-gen|
Avira : TR/AD.InstaBot.gzfzd
BitDefender : Gen:Variant.Midie.77297
Cyren : W32/Kryptik.COL.gen!Eldorado
Emsisoft : Gen:Variant.Midie.77297 (B)
ESET-NOD32 : A Variant Of Win32/Kryptik.HHYY
F-Secure : Trojan.TR/AD.InstaBot.gzfzd
Fortinet : PossibleThreat.ARN.M
Ikarus : Trojan.Win32.Ranumbot
Kaspersky : HEUR:Exploit.Win32.Shellcode.gen
Malwarebytes : Trojan.MalPack
McAfee : GenericRXMV-JU!F8EF98BBAFF6
Microsoft : Trojan:Win32/Glupteba.NA!MTB
Panda : Trj/Downloader.FUM
Sophos : ML/PE-A
Symantec : ML.Attribute.HighConfidence
TrendMicro : TROJ_GEN.R002C0DL420
Webroot : W32.Trojan.Gen
Backup your files
One important step before proceeding with the procedures below is to backup your files. Ransomware are not the same. Each has its unique sets of payloads aside from encrypting the files with complex method. Others tend to delete the infected files after certain period, while others keep them concealed on hidden places. In addition, ransomware decryption tools are not guaranteed to be perfect, there are instances that files suffer from damages during the decryption process.
So, create a backup copy of your entire Nobu encrypted files right now.
Nobu Ransomware Removal Guide
First thing to do is remove the Nobu virus before attempting the decryption. Remember that as long as the ransomware is active, it will repeatedly encrypt the files on the compromised computer.
Infection of Nobu ransom virus is dangerous to the system because it can inject files that runs each time Windows starts. To prevent the malicious files from loading, Windows operating system must run with minimal process and it can be done through SafeMode With Networking.
Quick Fix - Scan the PC with Combo Cleaner for Windows
Combo Cleaner is a trusted PC security and optimization tool equipped with powerful virus and malware detection engine. This program can get rid of ransomware like Nobu through this procedure.
1. Download the application from the following page:
2. Save the file to your preferred location.
3. Double-click the downloaded file CCSetup.exe and install with the default settings.
4. At the end of the setup process, click Finish to run Combo Cleaner.
5. The tool will update the signature file, please wait for this process to complete.
6. To begin checking for threats like Nobu, click on the Start Scan button. Wait for this scan to finish.
7. At the end of the scan process, click on Remove all threats to delete Nobu ransomware including all malicious objects from the computer.
Free features of Combo Cleaner for Windows include Disk Cleaner, Big Files finder, Duplicate files finder, and Uninstaller. To use antivirus, privacy scanner, and to delete identified threats, users have to upgrade to a premium version.
Please continue with the succeeding removal procedures if your are comfortable to manually get rid of the threat and malicious items linked with it.
Stage 1 : Temporarily Disable System Restore on Windows OS
Because Nobu and relevant virus is capable of reinstating itself by exploiting the System Restore of Windows, we suggests that you temporary disable System Restore while executing the steps. This option is also helpful to effectively run a full scan on the computer.Do not forget to enable back System Restore after completing the removal of Nobu ransomware. This feature is vital in reinstating the operating system to previous normal working condition in case of problems or conflicts occurs.
Stage 2 : Start Windows in Safe Mode With Networking
Windows 10/11 Guide
1. Click on Windows logo and select Power icon when options pop-ups.
2. Select Restart from the options while pressing Shift key on the keyboard.
3. Choose an Option window will appear, select the Troubleshoot button.
4. On next window, please choose Advanced Option.
5. On Advanced Option window, click on Startup Settings and then, click Restart button to reboot the computer.
6. When Windows boot on Startup Settings, press function key F5 or number 5 on keyboard.
A simpler alternative for Windows 10 users is to scan the computer with Microsoft Defender Offline. This will run a virus scan in the recovery environment.
Windows 8 Guide
1. Click Windows Start icon at the lower left section of the screen.
2. Open Search window and type Advanced in the field. It will open General PC Settings.
3. Click on Advanced Startup and then, click on Restart Now button.
4. Once the computer starts in Advanced Startup option menu, select Troubleshoot.
5. Next, click on Advanced Options to reveal the next section.
6. Click Startup settings and then, click Restart button to boot the PC in Startup Settings.
7. Use function key F5 or number key 5 to Enable Safe Mode with Networking.
Stage 3 : Scan the Computer with Sophos Antivirus
Ransomware files are placed deeply into the system and on various locations, thus, thorough scanning is vital to totally remove Nobu virus. Aside from our suggested tool, you may also run your own security program.
To remove Nobu automatically, scanning the computer with this efficient anti-malware tool is suggested. This scanner does not just uncover known threats like viruses or malware, it is also effective in discovering hazardous ransomware like Nobu.
1. Download Sophos Virus Removal Tool from the link below. Save the file on your computer where you can easily access it.
2. Once the download completes, browse the location of the file. Double-click to run the program and begin the install process.
3. On first windows of installation wizard, click Next to continue. Then, it will display the program’s License Agreement. You need to Accept the terms in order to proceed. If Windows prompts for User Account Control, please click Yes to proceed.
4. On succeeding windows, click Next or Continue to carry on with the installation. After completing the installation process, Launch Sophos Virus Removal Tool.
5. Internet connection is required when running this virus scanner in order to download important updates. Make sure that everything is up-to-date to effectively remove Nobu ransomware and other relevant viruses.
6. Click the Start Scanning button to inspect the computer. This will check the system for presence of malicious objects, malware, and viruses. The tool reveals items that were found linked to Nobu and other suspicious entities. Be sure to remove all identified threats.
The above procedures should have totally eliminated Nobu ransomware. However, if you found that there are still remnants of the virus, please proceed to succeeding procedures below.
Stage 4 : Double-check with Microsoft's Malicious Software Removal Tool
1. Download the free scanner called Malicious Software Removal Tool.
2. The tool automatically checks the operating system and suggest appropriate download version. Click on Download button to begin. Save the file to a convenient location, preferably on Desktop.
3. After downloading the file, Windows will prompt that download has completed. Click Run to start scanning for Nobu ransomware. Another option is to browse the location folder and double click on the file to run.
4. The tool will display Welcome screen, click Next. Please note the message "This tool is not a replacement for an antivirus product." You must understand that this program is made specifically to find and remove malware, viruses, Trojans, and other harmful elements on the computer. It was not designed to protect the computer.
5. Next, you will see Scan Type. Please choose Full Scan to ensure that all Nobu ransom virus entities and other harmful files left on the computer will be found and removed. For advanced computer user, you can opt for Customized Scan, if there are other drives or folders you wanted to include in this scan.
6. Full scan may take a while, please wait for Malicious Software Removal Tool to complete the tasks. However, you may cancel the scan anytime by clicking on the Cancel button.
7. After scanning, the tool will reveal all identified threats. There may be other threats that our first scan fails to detect. Please remove/delete all detected items.
8. When removal procedure is complete, you may now close Malicious Software Removal Tool. We hope that Nobu ransomware have been completely deleted from the computer. Please restart Windows to proceed with the normal operation.
Recover Files from Nobu Ransomware Infection
On this section, we will provide ways to decrypt files infected with Nobu ransomware. Aside from dedicated decryption software and common tools, other options for file recovery are provided. As much as we can, we will update this area whenever there is new and more suitable decryption tool was made available.
Decrypting Nobu infected files with Emsisoft Tools
This service from Emsisoft is helpful in unlocking encrypted files without paying the ransom. It gives three ways to detect the ransomware and provide suitable recovery method:
Upload ransom note – This is usually the .txt or .hta files that was generated by Nobu ransomware.
Upload the encrypted file – The actual encrypted file. Choose the one that is less than 8MB in size.
Contact information – Enter the email address or any links provided as it appears in the ransom note of Nobu virus.
After submitting any of the appropriate data, Emsisoft will attempt to identify the ransomware and provide keys if there are available.
Option 1: Windows Previous Version Tool
Windows Vista and Windows 7 have a feature called Previous Versions. However, this tool is only usable if restore point was made prior to ransomware infection. To use this tool as "recovery option" for files encypted by Nobu virus, please follow these steps:
1. Open My Computer or Windows Explorer.
2. Right-click on the affected files or folders. From the drop-down list, please click on Restore previous versions.
3. New window will open display all backup copy of files and folders you wanted to recover. Choose the appropriate file and click on Open, Copy, or Restore. Restoring selected files overwrites the current locked files on the computer. The tool is not actually recovering files encrypted by Nobu. Instead, it restores files from backup copy.
Option 2: Use ShadowExplorer to restore files encrypted by Nobu Ransomware
Just like Previous Version tool, ShadowExplorer is taking advantage of shadow copy created by Windows. This tool allows you to retrieve older version of files before it was encrypted by Nobu ransomware.
1. Download ShadowExplorer from the official web site.
2. Install the program with the default settings.
3. The program should run automatically after installation. If not, double-click on ShadowExplorer icon.
4. You can see the drop-down list on top of the console. Please select proper drive and the most recent point-in-time shadow copies of files you wish to restore prior to Nobu ransomware infection.
5. Right-click on the Drive, Folder, or File you wish to restore and click Export...
6. Lastly, ShadowExplorer will prompt for location where you want to save the copy of recovered files.
How to protect the computer from Nobu ransomware?
After the removal of the ransomware, it is important to prevent similar incident from happening again. In order to protect the computer effectively, computer user must know how Nobu ransomware was able to infect the computer. To minimize the possible infection, staying away from the common sources of this virus is crucial.
How Nobu ransomware can infect your computer?
The method of infecting the computers was found to be similar as other common viruses. Though, ransomware like Nobu is seen to have efficient deployment via spam email messages, web injectors, malicious software installers, misleading online advertisements, and through another virus infection.
Once the virus is executed, it immediately infects the system. Then, Nobu ransomware communicates to remote server so that unique key can be generated for the specific computer. After acquiring the key, it starts to decrypt target files using a complex method that is almost unbreakable. On the last stage of the attack, Nobu ransomware demands for ransom money as payment for the decryption tool. To further understand the attack scheme, we have included an infographic below.
Securing the computer against ransomware attack
Do a Regular File Back-up - Always backup your data on a separate storage devices such as external hard drives, optical discs, or online backup services.
Keep Your Software Updated - Make sure that you have the latest software updates especially on the operating system. Recent updates often contain vital security patches to help protect the computer against all forms of threats.
Install a Security Program - Protect the computer with effective anti-virus application using efficient real-time scanning. Regularly run a complete scan to check the computer for presence of malware.
Protect your files with Controlled Folder Access (Windows 10)
For Windows 10 users, aside from protecting the computer using anti-virus or anti-malware programs, one way to protect against ransomware attack is by using Controlled Folder Access. This feature of Windows Defender Security Center may not prevent the Nobu ransomware infection, but it can protect the folder and files in general. Follow the steps to enable Controlled Folder Access in Windows 10.
1. Go to Windows 10 Taskbar and search for Windows Defender Security Center.
2. Open Windows Defender Security Center and click on Virus & Threat Protection icon.
3. On next window, please click on Ransomware Protection.
4. Under Controlled Folder Access section, switch the slider to On. That will enable the feature and protect the folder against Nobu or any type of ransomware.
5. Click on Protected Folderslink to include additional folders. Make sure that folders where important files are located should be included in the list.
Certain programs maybe blocked by Controlled Folder Access feature. To fix the issue, simply have the specific program to be white listed.
1. Under Protected Folders, click Allow an app through controlled folder access.
2. Next, click the Add an allowed app and include the target executable file.
This Controlled Folder Access feature is one way to protect files against Nobu. Other important things to do in keeping files safe against ransomware is through early prevention like keeping programs updated, install an efficient security program, an do regular file backup on a separate media drive.