There are many ways to prevent a computer virus. However, if a computer becomes infected with a virus, it is important to understand that the computer’s hardware must be specifically designed for secure functioning in an environment with potentially hostile software. In the context of security, the term computer hardware is generally taken to mean ‘the computer’s central processing unit (CPU) or internal system bus (the CPU and internal system bus are the two main components of computer hardware). Hardware that has been specifically designed for secure functioning may contain features designed to prevent the running of unauthorized executables that try to access certain hardware facilities on the computer.