Preston does refer to the fact that Linux is pretty resistant to attacks, but it's instructive to not why this is so.
It's because Unix grew up in accademic environments, where hacking by hughly educated and motivated students with too much time on their hands is par for the course. Unix security was forged in the midst of the most hostile user environments on earth - college campus networks. The very first worms and viruses were essentialy unix software.
By comparrison, the environment in which MS Windows grew up - the ordered world of the company office, often without a network - was a cosy and relatively safe environment. It's only when the internet connected Windows PCs on cosy corporate and home networks to the wider world that they became vulnerable. I remember reading about unix viruses long before I encountered my first MS-DOS virus on a PC.
Unix and unix-like systems have much better in-built security because it's in their genetic heritage, and it got there through a ruthlessly Darwinian process.