Linux; the least safe server OS
Hardly news, but there's numbers to back it up now.
Linux accounts for 65.64% of manual intrusions in 24/7 online computing environments. Windows is at a steady 25.19% and BSD and Mac OS X is at 4.82%. These numbers are from the mi2g report “Deep study: The world's safest computing environment”. The conclusion:
“More and more smart individuals, government agencies and corporations are shifting towards Apple and BSD environments in 2004,” according to D. K. Matai, Executive Chairman, mi2g. “For how long can the truth remain hidden that the great emperors of the software industry are wearing no clothes fit for the fluid environment in which computing takes place, where new threats manifest every hour of every day. There is an accelerating paradigm shift visible in 2004 and busy professionals have spotted the benefits of Apple and BSD because they don't have the time to cope with umpteen flavours of Linux or to wait for Microsoft's Longhorn when Windows XP has proved to be a stumbling block in some well chronicled instances.”
They conclude this on the data from 235,907 successful intrusions, probably a high enough number to justify the 4 significant digits, statistically speaking.
The chief reason Linux is so bad is the way Linux distributors package the software in my opinion. It's a mess. I think I should spend a week-end writing a rant about that.