An ounce of prevention is worth a pound of cure
To understand how one goes about preventing spyware/adware from entering our system, one must understand where spyware/adware comes from. There are two main entry points for spyware/adware.
The first point of entry is free programs that people download off the internet from questionable sources. These programs almost always have spyware/adware, or worse, even Trojans bundled with them. Before you download anything from the web you must ask yourself a few simple questions. Do you trust this website? Do you really need this program? What's in it for them to offer this free software? For example, suppose you want to download Mozilla. Do you trust www.mozilla.org? Yes. Do you need this program? Yes. What's in it for them? Fame, glory, opposing the evil Microsoft monopoly. Now suppose you want to download a free screensaver program at some shady website. Do you trust the website? Questionable. Do you need this program? Not really. What is in it for them? There's no fame or glory, it's not an open source project. In most cases it comes down to money and by bundling spyware/adware in with their programs they can generate revenue to pay for the screensavers. Other common programs that bundle spyware/adware include file sharing programs, popup blockers, browser toolbars, etc.
The second point of entry is through your browser. A lot sites out there try to get you to say yes to spyware/adware. When you go to a site and it asks you to install a program you've never heard before in order to view the webpage, that is a major red flag. Yes there are legitimate browser extensions that you should install when it asks you like Macromedia Flash, or Adobe Acrobat Reader. But if you don't think you need it, just click no. Some sites are a bit trickier though. They will keep on asking you over and over again until you say yes. Here is the trick to get you out of that mess. Click no and quickly press the Alt-F4 key combination to close your browser before it asks you again.
WinXP SP2 - Warning Potential Spyware/Adware |
WinXP SP2 - Just Say No |
However, even if you are vigilant at saying no, some sites can still install their spyware/adware into your computer. Those sites are the shadiest, and they use security flaws in your browser to bypass your permissions and directly inject their evil software into your computer. There are two preventive measures you can take. First is to keep your browser updated to the latest version/patch. Second, do not visit questionable sites. Sites that offer free commercial software, or that is rated R are questionable sites.
Pre WinXP SP2 - Just Say No |
There are also some misconceptions I would like to clear up while I have your attention. First, a firewall will not protect you from spyware/adware. Why you ask.? It is because spyware/adware is invited in. Firewalls are good at blocking intruders from hacking in, but are useless at stopping you from downloading a spyware/adware infested program. Once the spyware/adware is in your system it can do whatever it wants however it wants whenever it wants. | 
