If you were using a fully updated version of Microsoft Internet Explorer last year, with every one of the patches installed, you could still have been vulnerable to attack from known flaws for 284 last year. For at least 98 of those days, Microsoft knew about bugs which were being actively exploited by criminals without a patch available. This means that there were only 81 days during which Internet Explorer was completely safe against known problems, compared to all but nine days for Mozilla Firefox. Apparently at least ten of the critical problems had resolutions published online before Microsoft released a fix, so perhaps Internet Explorer 7 will wield more security for users. Admittedly this research does not account for unknown bugs, so both browsers are likely to truly be vulnerable at any time.