There is a difference between unethical and illegal behavior. Ethics govern how people should behave, Laws in some sense how they must behave. Although there are good things in this view, the issues get very complicated. Genuinely criminal or unethical behavior sometimes follows in the guise of this belief. Viruses A virus is a program which infects other programs.
Viruses typically consist of two parts.
One part controls reproduction, spreading itself by copying onto floppy disks or email. The other part does something nasty or harmless to the computer system it is on. Typically viruses infect the operating system of the computer, which control everything, hence the possibility of serious damage. Initially, hackers created viruses to learn how they can be done, but now it is mostly vandelism, eg. Antivirus programs look for changes in operating system files, like their size or content, and use them to identify viruses.