In 2002 Microsoft issued 34 advisories for Windows XP, and 37 advisories for Windows 2000. By comparison, Red Hat Linux saw 87 advisories for its OS and Sun issued 83 alerts for Solaris.There's no mention of the severity of each security advisory or Windows 9x, but the numbers do suggest that Windows 2K/XP isn't as comparatively insecure as many alternative OS fans might have you believe. It is true that the media talks about Microsoft's security advisories far more than they do about advisories issued by Red Hat and Sun, but given the relative installation base of each OS, the focus is understandable.
Of course, just because Microsoft posted fewer security advisories doesn't mean that they have the more secure OS. Windows 2K/XP could have numerous security holes that have gone unpatched. Still, the numbers make me wonder if Microsoft's finally getting security right.