Symantec's regular "state of the nation" Internet Security Threat Report is always a good read.

Serendipity being what it is, I was reading the latest issue when I received the recently remade Dawn of the Dead (probably nowhere near as good as Romero's classic, but I'm a sucker for a good zombie movie), and the new series of Battlestar Galactica was premiering on Sky One. Trust me, there is a connection here.
One of the trends noted in Symantec's report is the growth in malware that creates networks of robots or zombie PCs; machines infected with remote-control hacks that lie dormant until the relevant control station sends out a command. Spammers are a major user of such "botnets", and pricing is keen: USA Today recently reported a 20,000 machine network offered for U.S. $2,000.
The prevalence of such networks reflects the sorry state of end user security, as the majority are stopped by up to date anti-virus and operating system patches. However, this situation is unlikely to improve in the short term. Indeed, with the move towards widely-networked games platforms such as the X-Box (a thinly disguised PC) and even the prospect of internet-savvy white goods, the zombie target base is expanding. If people don't patch their PCs, what chance do we have of them patching their games consoles and microwaves?
So much for zombies. The recently remade Battlestar Galactica has as its premise a devastating attack on the Good Guys by backdoors in their military software cunningly inserted by the machine-based Cylons. In a somewhat dramatic fashion the show illustrates the dangers of the totally networked environment: when things go wrong, they can go wrong everywhere and they can go wrong fast. In safety systems parlance this is known as "tight coupling" and it often magnifies relatively small problems into major catastrophes.
So what to do? Well, the introduction of "firebreaks" that interrupt the tight coupling is possibly the best solution. The problem is balancing the need for connectivity with this sort of isolation which inevitably interferes with great benefits of networks. Unfortunately, at the moment the impetus appears to be to global connectivity without much thought to the consequences.
It's been said that the power of a network increases with the number of connections, but so does the vulnerability. Ignore it at your peril – the Cylons and Zombies are waiting.