alt Hacker NewsFun fact: you don't get rid of them even when you put a captcha on all visitors from Singapore. I still see a spike in traffic that perfectly matches the spike in served captchas, but this time it's geographically distributed between places like Iraq, Bangladesh and Brazil.
Hopefully it at least costs them a little bit more.
Usually, there are multiple layers of different counter-protection measures. If you block by country, they shift to different IP ranges, if you block by IP, they might use a new IP for every request, and escalate further depending on the bot owner and your actions.