Viruses

Viruses are programmes reproducing themselves and spreading attached to other host programmes of an information system. An open communications network, like Internet, provides them an excellent basis for diffusion all over the world. Viruses may weaken the accessibility, integrity and confidentiality of the data in an information system, i.e. they can destroy, change or modify the data in the information system. The viruses may also disturb other operations in the information system, for instance to slow down or make difficult the use of the system or the functioning of the operating system.

Virus needs a host programme to spread, for instance macros in word processing programmes and programmes to be performed can serve as host programmes.