IE provides the biggest payoff for malicious hackers who set out to exploit its flaws.

The biggest problem with IE is its reliance on Microsoft’s ActiveX technology, which allows Web sites to run executable programs on your PC via your browser. Security patches and upgrades, including Windows XP’s Service Pack 2 and the recently released IE 7, make ActiveX safer, but the inevitable flaws that allow malware to circumvent those security measures–combined with the reality that we computer users are often a credulous lot–make ActiveX a risk not worth taking. Happily, with very few exceptions (such as Microsoft’s Windows Update site), you can browse the Internet effectively without ActiveX.