I host a forum where the target audience is ONLY U.S., Australia, and Oceania. I would like to know how I could ban all other countries from access to my forum except the three above. I've been having a problem with bots signing up and they are all coming from IPs from other countries, so I think this would fix the problem and would not bother my target audience.
Is there an easy way to do this? Advice would be appreciated.
Bots use proxy servers all around the world. People running bots know how to get around IP blocking.
Using GeoIP to prevent bots from signing up on your system will not really solve the core problem.
Captcha can help to some extent, however it's actually been broken (in the sense that well programmed bots can solve Captcha challenges) for several years.
The StackOverflow model is actually very good... don't let a new user do very much until they get a little bit of reputation (e.g. post something that gets upvoted by other users, or require the first few posts to receive moderator approval).