Here's a top ten list of the most common ways intruders target your computer:

1. Hackers—A hacker is someone trying to gain unauthorized access to a computer or network.
2. Hijackers—Hijacking is a type of attack in which an attacker gets access to communication between two people or machines and then pretends to be one of them.
3. Viruses—Like many viruses that make you sick, computer viruses are easily spread. The term virus is used for a piece of computer code that attaches itself to a program or file so it can spread from computer to computer, usually meant to do damage to your software, hardware and files.
4. Worms—A worm, like a virus, is designed to copy itself from one computer to another, but it does so automatically.
5. Spyware—Spyware is software that performs certain behaviors, such as filling your screen with advertising popups (such programs are known as adware), collecting or transmitting personal information (through keystroke loggers), or changing the configuration of your computer, generally without your consent.
6. Malware—Malware is short for "malicious software" that is designed to cripple your computer or destroy your information.
7. Trojan horses—Like the Trojan horse of old, when soldiers hide inside a fake statue to attack the city of Troy, today's Trojan horses hide malicious software within other seemingly harmless software.
8. KeyLogger—a piece of software which captures a user's strokes on a computer keyboard. This software can be distributed through a trojan horse or virus to hack into an capture private information from an unsuspecting user.
9. Bots—A bot is a type of malware which allows an attacker to perform actions using your computer, usually without your knowledge.
10. Botnets—Botnets are composed of individual bots-sometimes numbering in the hundreds of thousands. They are then used to distribute spam e-mail, spread viruses, and attack other computers and servers.