There's a scumware plague at the moment. All it takes is a visit to a pushy web site or a "loaded" shareware install, and next minute your Internet Browser homepage has been changed, your default search setting altered, unwanted ads pop up on your screen, and worse.

If you use Windows 2000 or later, my top recommendation for safe browsing is a free program called Sandboxie that creates a special contained "sandbox" environment on your PC. While browsing within the virtual sandbox provided by Sandboxie, you are totally corralled off from other parts of your PC. So any files you download are isolated to the sandbox. Similarly, any programs that are executed only do so within the sandbox, and have no access to your normal files, the Windows operating system or any other part of your PC.

Usage is remarkably simple. To start a sandboxed browsing session, you just click the Sandboxie icon from the Quick Launch tray and this will launch your default browser in the sandbox. You can then use it in the normal way to browse to sites or download files, but be aware that the sound may be muted in that video file you're about to view.

If you download a file, it will install normally but, again, will be corralled off from your real PC, because any new processes running in your computer memory or entries in the Windows startup areas will be sandboxed.
 
After you have finished browsing, you can right click the Sandboxie icon and delete all sandboxed files and processes, and your PC will be returned to much the same state it was in before the browsing session. If you want to retain particular downloaded files, you can save them permanently before clearing the contents of the Sandbox.

The advantage is clear: any spyware, trojans, keyloggers or other malware products that "infected" your PC while browsing will be eliminated.

Sandboxie works fine with all browsers but requires Windows 2000 and later. It can cause problems on some PCs so backup before installing.

Users of earlier Windows versions may want to check out SpywareBlaster. It's not a sandbox but is, rather, a free program that changes some settings in your computer to help prevent an initial infection. It provides protection against thousands of malevolent products that use ActiveX based exploits, and can block hostile sites and discard unwanted cookies as well.

SpywareBlaster is most effective with Internet Explorer, but can be used with Firefox also, though this may be overkill because Firefox doesn't need to be protected against ActiveX exploits. Once it has changed your settings SpywareBlaster doesn't really need to continuously run on your PC other than to provide updates. These can be initiated manually, or you can opt for the automatic update service which costs $9.95 annually.

A companion program to SpywareBlaster is SpywareGuard, which provides active protection. It's a monitor that checks programs for malware behavior before they are run, and also does some signature checking as well. However, of late SpywareGuard seems to have been rather neglected, with no new updates for more than a year, so it's up to you to use it !!!.

http://www.sandboxie.com  Free for personal use, Win2K and later, 310KB
http://www.javacoolsoftware.com/spywareblaster.html  Freeware, all Windows versions, 2.5MB http://www.javacoolsoftware.com/spywareguard.html  Freeware,  All Windows versions, 913KB