The number of security holes that occur isn't as telling as how they're handled.

Here is the skinny.  FireFox actually has more security issues than Internet Explorer, but the thing is that it usually takes Microsoft weeks to fix security issues.  This gives malicious code writer PLENTY of time to create and distribute something juicy. 

"Mozilla is forthcoming about vulnerabilities," Levy said, whereas "it takes Microsoft far longer to acknowledge vulnerability."

Now here is another thing about Microsoft (and CISCO) they lie and cover up some of the security flaws.  This is probalby because of reputation and shareholder protection or who knows what other beauracracy and formalities.. but FireFox is very fast. 

I was at Defcon 11 and I recall some Gray Hats found a few flaws in Microsoft products (serious ones... nothing new about that).  They attempted to submit these flaws to Microsoft and other companies and were completely ignored.  Sometimes it seems giant corporations can only put out fires instead of prevent them.

Here is an example of how slow the Microsoft people are on security ---> 6 Month old exploit.

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