Programs installed on your computer that collect information on you are called spyware or adware. Most often, the information being recorded is details on your buying or web browsing habits. Generally, sharing this information is not dangerous but is a violation of your privacy unless you have consented. Spyware and adware can do much more invasive things, however. More malicious programs can record what you type, look for information on your hard drive, give away your e-mail address, or read encrypted communications.

Spyware, also called adware, is a name used for programs that collect information on you or your computer. These programs do a variety of things. Some simply sit in the background while they collect data and send this information to marketing companies. It is also common for spyware to display unwanted pop-up ads on your computer. Other types of spyware will redirect your web browser to unwanted web sites, or add toolbars and icons to your web browser.

Spyware is often bundled with free programs, such as file-sharing programs or programs that offer services to display weather information in your toolbar. The program may even tell you what information it is collecting and how the information is being used when you install it.

The bottom line is that it's hard for you to verify if a piece of spyware is as benign as it claims. Often, it is difficult to understand from the license agreement exactly what information they are collecting. For example, Marketscore is a program that offers to speed up your web browsing in return for your permission to monitor what sites you visit. It doesn't make clear that its method of monitoring the sites you visit allows it to read encrypted communications with secure websites, such as your bank's website or OneStop.

Be careful what software you install on your computer. This includes free screensavers, weather bugs, games, and file-sharing programs. Do not download software from web sites you don't trust. If you have questions about whether or not to trust a web site, ask for help. Don't click on links inside pop-up windows or ads, including buttons that say 'Close'. Even ads that offer anti-spyware products may install spyware.

While most spyware requires you to download or click something before it can be installed, some programs take advantage of security holes in the software on your computer. Keep all software updated with the latest patches available from the vendor.

The Firefox web browser is a good alternative to Internet Explorer. Using a personal firewall can also help. A firewall is a program that watches how your computer connects to the Internet and what other computers are trying to connect to your computer. One may be installed by default with your system, Mac OS X and Windows XP come with a built-in firewall. There are also commercial and non-commercial products available.

How do I know if I have spyware on my computer?
Common symptoms of spyware are: a computer running slowly, a barrage of pop-up ads, new toolbars or icons in your web browser, your web browser visiting sites you didn't select, or changes in the homepage you set in your browser. Even if you haven't noticed any of these symptoms it is a good idea to scan your computer for spyware on a regular basis.

There are a number of tools that can be used to scan your computer for spyware. Products like Ad-Aware, released by Lavasoft, have a version that is free for personal use. SpyBot Search & Destroy is another available product. For Macintosh computers, a product called MacScan is available. As with all software, download only from trusted sites.