There's a lot of malware out there, and that's a major nuisance, but here's a glimmer of good news: Australians are a bit less likely than the average netizen to end up with viruses or other nasties on their systems.
According to Microsoft's latest Security Intelligence Report -- based on machines on which its Malicious Software Removal Tool has been run -- around 3.9 out of every 1000 PC systems in Australia are infected with some sort of malware. The global average is 8.7. Whether that's because we're more aware of the risks, or because our slow broadband connections mean we're not always able to finish downloading trojans and the like, remains debatable.
At any rate, it's potentially good news if you buy into the argument that you don't need to pay for security software (personally, I'm not fully convinced). Of course, the likelihood is that the infection rate is actually higher, since people who haven't run MSRT or another tool are likely continuing in blissful ignorance of their bot-infected ways.