Index - expand your thinking

When you execute a program code that's infected by a virus, the virus code will also run and try to infect other programs, either on the same computer or on other computers connected to it over a network. And the newly infected programs will try to infect yet more programs. When you share a copy of an infected file with other computer user, running the files may also infect their computers; and files from those computers may spread the infection to yet more computers.

How can emails spread viruses?

You can't get a virus just by reading a plain text email message. What you need to watch out for are messages that include an executable file attachment ( maybe an encoded programme or an infected word document) or in some cases encoded messages containing embedded executable code ( JavaScript in an HTML message).