Some of you may have seen an Australian IT article reporting that Australia's anti-spam laws appear to be having an impact. Spam from Australia has decreased significantly. This is confirmed by Spam Haus.
While it does appear that the laws have driven some Australian based spammers away, I am wondering if there isn't another variable that's also impacting things. Back in May/June, BigPond blocked access to TCP/IP port 25 across its network. Unless your computer was talking to one of the BigPond mail servers, you kept getting errors when trying to send emails (business accounts could request that access not be blocked so they could use their own mail servers, etc). This change certainly impacted those staff at my office who were using their personal BigPond accounts when travelling - no more sending mail via our server when out on the road. Ooops...
According to an article in The Register, it is estimated that about 80% of all spam is sent from "zombies", aka machines that have been infected by the latest viruses/worms, all of which open "back doors" that turn the machines into willing spambots. Given this, I really think that BigPond's actions may have also contributed to the drop, not just the new law, after all, BigPond were always getting into trouble with the rest of the 'net because they were seen as a major source of spam from Australia (ranging from not turning them off when found through to actively working with some spammers). They're also a favourite ISP for many people who are likely targets for "zombification" - eg: home users on broadband connections without firewalls, latest service packs, virus scanners, etc.
To me, this all says that while the new law may be helping, it's not the sole reason that spam from Australia has dropped off so dramatically. Food for thought.