Vunet.com reports that attacks on *nix based systems increase, while attacks on Windows/IIS decrease.

Taken from vunet.com article:
Attacks on Linux and open source systems are set to more than double this year and may even eclipse the number of hostile attempts made on Windows systems in the future. [...]

In the first six months of this year 7,630 overt attacks have taken place on Linux boxes. The total number of attacks last year amounted to 5,736.

But attacks on Windows/IIS systems have already dropped by 20 per cent on last year's figures, from 11,828 to 9,404.

According to mi2g, the big picture shows that hack attacks in general are on the rise, up 27 per cent on last year, from 16,007 to 20,371.
My thoughts on this: Open Source software has grown to a state where-in it is possible for other than expert users to setup, use and maintain a system. One could state that with a growing pool of Open Source users, the average computer know-how of a single user decreases. Because of this, more configuration errors and security flaws (in the users system configuration) tend to be overlooked, thus explaining the numbers in the article quoted.

Related links:
http://www.vnunet.com/News/1133518
http://slashdot.org/articles/02/07/1....shtml?tid=172