Earlier this week, Apple announced that sales of Mac OS X 10.5 (Leopard) during its launch month topped sales for its predecessor. At the same time, ZDNet's George Ou says the Mac OS, which customers perceive as more secure than other operating systems, actually had more publicly reported vulnerabilities in 2007 than Windows XP or Windows Vista:
I used vulnerability statistics from an impartial third party vendor, Secunia, and I broke them down by Windows XP flaws, Vista flaws, and Mac OS X flaws. Since Secunia doesn't offer individual numbers for Mac OS X 10.5 and 10.4, I merged the XP and Vista vulnerabilities so that we can compare Vista + XP flaws to Mac OS X ... So this shows that Apple had more than 5 times the number of flaws per month than Windows XP and Vista in 2007, and most of these flaws are serious.
However, as ZDNet UK writer Tom Espiner points out in this piece, many people don't think the number of vulnerabilities an OS has is an accurate measure of its security. For example, he says:
Tristan Nitot, president of Mozilla Europe, told ZDNet.co.uk this month that it was more important to take into account the time it takes to patch vulnerabilities.
The amount of exploit code available is also relevant, and Mac OS X exploit code "in the wild" is rare, says Espiner.