Australian trademark and copyright laws?

I am an Australian making an original computer game which I eventually intend to sell via digital distribution. I understand Australia has an automatic copyright system to protect intellectual property, but does this extend to unique character names/designs, or do I need to trademark these names and their likenesses? As I plan to sell the game online, how can I implement an international copyright and trademark of my work - or does the Australian law protect me also from international intellectual property thieves?