Remove CTB-Locker and Restore the Encrypted Files

Berta Bilbao

Berta is a dedicated malware researcher, dreaming for a more secure cyber space. Her fascination with IT security began a few years ago when a malware locked her out of her own computer.

More Posts

CTB-Locker, also known as Critoni Ransomware, is a Trojan that encrypts the files on the infected computer and blocks the user’s access to his data. Critoni Ransomware displays a ransom message demanding a high price for the decryption of the files. As researchers have established, the crypto-malware has been for sale on the black market for around 3000 US dollars. Experts warn that the threat is still actively infecting computers worldwide and recommend installing a trustworthy anti-malware tool no your machine and performing regular backups of your important files.

CTB Locker – How Did I Get Infected

CTB Locker has been reported by Microsoft Malware Protection Center to be spread via exploit kits or a Trojan.Downloader. Exploit kits may be created for plugins such as Java or Flash Player and it is easy to insert malicious code that creates weaknesses in Windows. Furthermore, the Trojan.Downloader that may be used might collect different information about the computer that will be infected so that the infection process is undetected. Such information may be details about the Windows version, type of Antivirus software used, etc. The Trojan may spread via malicious links that may contain drive-by-downloads or malicious attachments sent online.

CTB Locker Ransomware – What Does It Do?

Once it has been downloaded and activated, the ransomware may insert malicious code into the critical Windows process, called svchost.exe. Furthermore it may create randomly named files, such as sz0s8g2h.exe for example, in the following folders:

• %Temp%
• %AppData%

According to Microsoft researchers, after it has created its payload files, the ransomware begins to scan for and encrypt files with these file extensions:

→3fr 7z abu accdb ai arp arw bas bay bdcr bdcu bdd bdp bds blend bpdr bpdu bsdr bsdu c cdr cer config cpp cr2 crt crw cs dbf dbx dcr dd dds der dng doc docm docx dwg dxf dxg eps erf fdb gdb groups gsd gsf ims indd iss jpe jpeg jpg js kdc kwm md mdb mdf mef mrw nef nrw odb odm odp ods odt orf p12 p7b p7c pas pdd pdf pef pem pfx php pl ppt pptm pptx psd pst ptx pwm py r3d raf rar raw rgx rik rtf rw2 rwl safe sql srf srw txt vsd wb2 wpd wps xlk xls xlsb xlsm xlsx zip

After encrypting the files of users, it may add a suspicious file extension after the files. The following file extensions are reported by researchers from Microsoft and BleepingComputer to be used by CTB Locker:

• .ctb
• .ctb2
• .ctbl
• Random file extensions(newer versions)

The ransomware then may drop the following files that contain the demands of the cyber-criminals:

• %MyDocuments%\AllFilesAreLocked{randomuserid}.bmp
• %MyDocuments%\{randomname}.html
• %MyDocuments%\DecryptAllFiles{randomuserid}.txt

These files contain the ransom instructions. One of them is the wallpaper that is changed to the following:

The encrypted files contain a decryption key held by the cyber criminals. As other ransomware Trojans, CTB-Locker uses Onion routing (Tor) in order to remain anonymous and protect the cyber-crooks’ identity. The good news is that compared to other crypto-viruses, CTB-Locker does not demand a ransom this high. The ransom amount demanded is 0.2 Bitcoins which is around 120 US dollars.

What is new about this ransomware is that the new variants may use random file extensions to encrypt the files such as .zz2dqj or .9jsaxsf. Upon opening, Windows claims that the questionable files are corrupt, and they cannot be fixed by simply removing the extension for the file. Here is an example of an encrypted file names by CTB-Locker:

• New Document.docx.ctbl
• New Picture.jpg.ctb
• New Presentation.pptx.ctb2
• New Text Document.vdi.adid2k

Even though paying the ransom money may bring back your files, we strongly advise you NOT to do it, even though the newer variant of CTB decrypts 5 files for free. This funds the cyber-criminals to develop further their virus plus it may be no guarantee that the decryption keys for your files will be sent back to you so you can restore them.

Here is the decryption screen users see when they are following the decryption instructions:

Source: Bleeping Computer

Removing CTB-Locker Ransomware Completely

To remove this nasty ransomware virus, you should boot your PC into safe mode and install an anti-malware scanner that will locate its registry entries and restore any scheduled tasks for the malware to run on system start. For maximum effectiveness, it is advisable to download the anti-malware software from a safe PC and install it via offline installer to the infected one while you are offline.

1. Boot Your PC In Safe Mode to isolate and remove CTB-Locker

1. Boot Your PC Into Safe Mode

1. For Windows 7,XP and Vista. 2. For Windows 8, 8.1 and 10.

For Windows XP, Vista, 7 systems:

1. Remove all CDs and DVDs, and then Restart your PC from the “Start” menu.
2. Select one of the two options provided below:

– For PCs with a single operating system: Press “F8” repeatedly after the first boot screen shows up during the restart of your computer. In case the Windows logo appears on the screen, you have to repeat the same task again.

– For PCs with multiple operating systems: Тhe arrow keys will help you select the operating system you prefer to start in Safe Mode. Press “F8” just as described for a single operating system.

3. As the “Advanced Boot Options” screen appears, select the Safe Mode option you want using the arrow keys. As you make your selection, press “Enter“.

4. Log on to your computer using your administrator account

While your computer is in Safe Mode, the words “Safe Mode” will appear in all four corners of your screen.

Step 1: Open the Start Menu

Step 2: Whilst holding down Shift button, click on Power and then click on Restart.
Step 3: After reboot, the aftermentioned menu will appear. From there you should choose Troubleshoot.

Step 4: You will see the Troubleshoot menu. From this menu you can choose Advanced Options.

Step 5: After the Advanced Options menu appears, click on Startup Settings.

Step 6: Click on Restart.

Step 7: A menu will appear upon reboot. You should choose Safe Mode by pressing its corresponding number and the machine will restart.

2. Remove CTB-Locker with SpyHunter Anti-Malware Tool

2. Remove CTB-Locker with SpyHunter Anti-Malware Tool

1. Install SpyHunter to scan for and remove CTB-Locker.2. Scan with SpyHunter to Detect and Remove CTB-Locker.

Step 1:Click on the “Download” button to proceed to SpyHunter’s download page.

It is highly recommended to run a scan before purchasing the full version of the software to make sure that the current version of the malware can be detected by SpyHunter.

Step 2: Guide yourself by the download instructions provided for each browser.
Step 3: After you have installed SpyHunter, wait for it to automatically update.

Step1: After the update process has finished, click on the ‘Scan Computer Now’ button.

Step2: After SpyHunter has finished scanning your PC for any CTB-Locker files, click on the ‘Fix Threats’ button to remove them automatically and permanently.

Step3: Once the intrusions on your PC have been removed, it is highly recommended to restart it.

3. Back up your data to secure it against infections and file encryption by CTB-Locker in the future

3. Back up your data to secure it against attacks in the future

Security engineers recommend that you back up your files immediately, preferably on an external memory carrier in order to be able to restore them. In order to protect yourself from CTB-Locker (For Windows Users) please follow these simple steps:

1. For Windows 7 and earlier 1. For Windows 8, 8.1 and 10 1. Enabling the Windows Defense Feature (Previous Versions)

1-Click on Windows Start Menu

2-Type Backup And Restore
3-Open it and click on Set Up Backup

4-A window will appear asking you where to set up backup. You should have a flash drive or an external hard drive. Mark it by clicking on it with your mouse then click on Next.

5-On the next window, the system will ask you what do you want to backup. Choose the ‘Let Me Choose’ option and then click on Next.

6-Click on ‘Save settings and run backup’ on the next window in order to protect your files from possible attacks by CTB-Locker.

1-Press Windows button + R

2-In the window type ‘filehistory’ and press Enter

3-A File History window will appear. Click on ‘Configure file history settings’

4-The configuration menu for File History will appear. Click on ‘Turn On’. After its on, click on Select Drive in order to select the backup drive. It is recommended to choose an external HDD, SSD or a USB stick whose memory capacity is corresponding to the size of the files you want to backup.

5-Select the drive then click on ‘Ok’ in order to set up file backup and protect yourself from CTB-Locker.

1- Press Windows button + R keys.

2- A run windows should appear. In it type ‘sysdm.cpl’ and then click on Run.

3- A System Properties windows should appear. In it choose System Protection.

5- Click on Turn on system protection and select the size on the hard disk you want to utilize for system protection.
6- Click on Ok and you should see an indication in Protection settings that the protection from CTB-Locker is on.

Restoring a file via Windows Defense feature:
1-Right-click on the encrypted file, then choose Properties.

2-Click on the Previous Versions tab and then mark the last version of the file.

3-Click on Apply and Ok and the file encrypted by CTB-Locker should be restored.

Optional: Using Alternative Anti-Malware Tools

4. Remove CTB-Locker Using Other Alternative Tools

Malwarebytes Anti-MalwareSTOPZilla Anti Malware

1. Install Malwarebytes Anti-Malware to scan for and remove CTB-Locker.
Step 1: Download Malwarebytes by clicking here.
Step 2: A pop-up window will appear. Click on the ‘Save File’ button. If it does not, click on the Download button and save it afterwards.


Step 3: After you have downloaded the setup, simply open it.
Step 4: The installer should appear. Click on the ‘Next’ button.

Step 5: Check the ‘I accept the agreement’ check circle if not checked if you accept it and click the ‘Next’ button once again.

Step 6: Review and click on ‘Next’ on the following 4 steps that will appear afterwards and after that click on the ‘Install’ button.

Step 7: After the installation process has completed click on the ‘Finish’ button and check the ‘Launch MalwareBytes AntiMalware’ check box.

2. Scan your PC with MalwareBytes to remove all CTB-Locker associated files automatically.

Step 1: Launch MalwareBytes if you havent launched it after install.
Step 2: Wait for the software to update and then click on the blue ‘Scan Now’ button. If it doesnt start updating automatically, click on the blue ‘Update Now’ highlighted text.

Step 3: At this point, after clicking the ‘Scan Now’ button, the system should start scanning your PC. It may take a while but be patient – it is worth it.

Step 4: After the scan has been complete and all of the threats have been identified, click on the ‘Remove Selected’ button to delete them permanently.

Step 5: Once the scan has completed, MalwareBytes will prompt you to restart your computer. It is recommended to save all your data you are working on before restarting.

1. Download and Install STOPZilla Anti-malware to Scan for And Remove CTB-Locker.
Step 1: Download STOPZilla by clicking here.
Step 2: A pop-up window will appear. Click on the ‘Save File’ button. If it does not, click on the Download button and save it afterwards.

Step 3: After you have downloaded the setup, simply open it.
Step 4: The installer should appear. Click on the ‘Next’ button.

Step 5: Check the ‘I accept the agreement’ check circle if not checked if you accept it and click the ‘Next’ button once again.

Step 6: Review and click on the ‘Install’ button.

Step 7: After the installation process has completed click on the ‘Finish’ button.

2. Scan your PC with STOPZilla Anti Malware to remove all CTB-Locker associated files completely.
Step 1: Launch STOPZilla if you haven’t launched it after install.
Step 2: Wait for the software to automatically scan and then click on the ‘Repair Now’ button. If it does not scan automatically, click on the ‘Scan Now’ button.

Step 3: After the removal of all threats and associated objects, you should Restart your PC.

Restore Files Encrypted by CTB-Locker Ransomware

Security engineers strongly advise users NOT to pay the ransom money and attempt restoring the files using other methods. Here are several suggestions:

To restore your data, your first bet is to check again for shadow copies in Windows using this software:

Shadow Explorer

If this method does not work, Kaspersky have provided a decryptors for files encrypted with the RSA and other encryption algorithms:

Kaspersky Decryptors

Another method of restoring your files is by trying to bring back your files via data recovery software. Here are some examples of data recovery programs:

EaseUS Data Recovery
Recuva
R-Studio
Photorec

For further information you may check the following articles:
Remove RSA-2048 Key From Crypto Ransomware
Restore Files Encrypted via RSA Encryption

Berta Bilbao

Berta is a dedicated malware researcher, dreaming for a more secure cyber space. Her fascination with IT security began a few years ago when a malware locked her out of her own computer.

More Posts