Ransomware is a category of malware that demands compensation for data or functionality that it holds hostage. It will very often block access to the PC, and only allow the user to access the web to pay the ransom. Norman security software detects millions of ransomware variants, but every day hundreds of new variants are created.
If your PC has been infected it will often be very hard to perfom tasks like running virus scan or downloading removal tools, as the malware will block access to the PC.
In such cases most infections can be cleaned using the built in System Restore tool in Windows following these instructions:
1. Boot your PC into Safe Mode with Command Prompt (tap F8 continously during startup to access the startup menu).
2. Type the command cd\, press Enter
3. Type the command cd windows\system32\restore, press Enter
4. Type the command rstrui, press Enter
5. Follow the instructions to restore your system to a date prior to the infection
6. Download and run Norman Rescue Disk. Run a Full scan of your system.