If phishing is the digital equivalent of someone stealing your credit card number, spyware and viruses are like having criminals living in your bedroom. (Spyware is software that monitors and records everything you do, and a virus is a program that deletes files or causes other damage.) Unlike phishing scams, both spyware and viruses actually live on your computer. These types of infections typically find their way onto your computer through a malicious file you download. The bottom line is this:
You should never, ever download a file unless you know exactly what it is, where it's coming from, and whether the person or company offering it is trustworthy.
Unfortunately, many browsers make it easy to download files inadvertently in the form of extensions. In Internet Explorer, for example, a Web site can spit out a big, annoying confirmation window as soon as it loads. If you click Yes in a hurry to get to the page, a malicious extension is installed. Firefox does everything it can to prevent you from installing malicious files inadvertently. Instead of allowing Web sites to get in your face with extension downloads, Firefox displays the non-intrusive toolbar that you see in Figure 15-9. (This toolbar doesn't appear for the official Firefox site, though.)
Figure 15-9: Firefox displays this toolbar at the top of Web sites that try to install a browser extension.
Note that the mere appearance of this toolbar doesn't necessarily suggest impropriety on the part of the Web site. The toolbar appears whenever a Web site other than the official, trusted Firefox Plugins Web site (http://addons.mozilla.org) tries to install an extension. If you trust the Web site you're viewing, go ahead and proceed, as I discuss in Chapter 20 in the section on installing from another site.
Firefox does everything it can to keep you safe, but your computer has many borders to protect, and the browser is only one of them. You must install three additional tools to remain safe and sound on the Internet:
Antivirus software: This tool monitors the files on your computer and checks newly downloaded files for viruses. If it finds one, it notifies you immediately and allows you to either delete the file or quarantine it so it can't harm your computer. It's critical that you keep your antivirus software up-to-date because new viruses are discovered regularly. Recommendations: Norton AntiVirus and McAfee VirusScan are available in stores.
Antispyware software: Like antivirus software, this tool monitors the files on your computer as well as new downloads, but it's looking for spyware. If it finds any, it notifies you immediately and allows you to delete the file. You must also keep your antispyware software up-to-date because new spyware threats are discovered regularly. Plenty of high-quality antispyware tools are available free of charge, although many antivirus suites (which usually cost money) include them nowadays. Recommendations: Ad-Aware is freely available from Lavasoft (http://www.lavasoftusa.com/software/adaware), and Spybot-Search & Destroy is freely available from http://www.safer-networking.org/en/download.
Firewall: A firewall monitors inbound and outbound Internet connections on your computer — that is to say, it checks when your computer tries to connect to the Internet, and when other computers try to connect to yours. The newest versions of Windows, XP and Vista, come with a built-in firewall that is on by default, so you don't have to do anything. Recommendation: If you have an older version, I recommend ZoneAlarm, available from http://www.zonelabs.com.
Additionally, you should install new security patches for your computer as soon as they're available. See http://microsoft.com/security for more information about the Windows patching process, or http://www.apple.com/support/downloads for the latest Macintosh security patches.