These days, the biggest danger you face when you go onto the Internet might be spywarea type of malicious software that can invade your privacy and wreak havoc on your PC. Spyware is a relatively new phenomenon; it does not have a long history as do viruses, Trojans, and worms.
Spyware is an umbrella name for many types of malicious programs, but these kinds of programs have several things in common. First, all of them, one way or another, spy on your behavior. They may watch which web pages you visit and report that information to a server or person, or they might track your web searches. They may even allow people to record every keystroke you make or open a back door into your computer so hackers can later take control of your PC when they want.
The second thing they have in common is that they install either without your knowledge or by tricking you. One common way they get on your PC is when you install a piece of software, such as file-sharing software. When you install that software, spyware often comes along for a ride and installs itself without your knowledge or misleads you about what the program actually does.
Although some spyware is created for purely malicious reasons, other kinds are created as part of money-making schemes. One kind of spyware swarms your PC with dozens of pop-up ads, some of which you'll most likely click to close. But every time you click, the spyware purveyor makes money because he has a business arrangement with a merchant or website to drive traffic to it.
There is a fine line between spyware and what is called adware. They work similarly, but with adware, you download a piece of software that you can use for free, such as a weather program. In return, the adware watches your surfing habits and sends that information to a server, which then delivers ads to you based on your behavior. The ads are displayed only inside the weather program and don't appear when you don't use it. Spyware, by way of contrast, watches you all the time and displays ads whenever you surf the Web or are connected to the Internet.
Spyware can do more than just spy on you. It can do damage to your computer as well. Some spyware inundates your computer with blizzards of pop-up adsin some instances so many that it takes away all your system resources and your PC grinds to a halt. This makes your computer unusable.
Because there is money to be made from surfing, spyware isn't going away any time soon. But as you'll see in this chapter, anti-spyware can combat it, so there are ways to keep yourself safe and protect your privacy.