Windows 8 Bible

Types of Malware

Malicious software comes in many forms. All forms have certain things in common, however. For one, they’re invisible — you don’t even know they’re there. For another, they all do something bad, something you don’t really want happening on your computer. Third, they’re all written by human programmers to intentionally do these bad things. The differences have to do with how they spread and what they do after they’re on your computer. We tell you about the differences in the sections that follow.

Viruses and worms

Viruses and worms are self-replicating programs that spread from one computer to the next, usually via the Internet. A virus needs a host file to spread from one computer to the next. The host file can be anything, although viruses are typically hidden in e-mail attachments and programs you download.

A worm is similar to a virus in that it can replicate itself and spread. However, unlike a virus, a worm doesn’t inject itself into another file to infect your computer. It can go from one computer to the next right through your Internet connection. That’s one reason it’s important to always have a firewall up when you’re online — to keep out worms that travel through Internet connections. For more on firewalls, see Chapter 9.

The harm caused by viruses and worms ranges from minor pranks to serious damage. A minor prank might be something like a small message that appears somewhere on your screen where you don’t want it. A more serious virus might erase important ...