I don't know exactly how this forum protects itself against 'bots', that is software written to penetrate websites for the purpose of planting malware, advertisements, scams and other nastiness.
However, a common counter-measure is for the site to confirm new members are human by getting them to jump through a few simple hoops before giving full privileges. After registering, the extra steps are complicated enough to fool a bot, but hopefully not complicated enough to annoy genuine new members! The exact method isn't advertised, and is periodically changed, because that would give a bot programmer enough information to pick the lock.
Typically, proof of humanity is provided by insisting new members make a few posts, perhaps introducing themselves and saying hello. Nothing difficult about the posts, short and simple should do the trick, there's no need to write a complicated essay!
Dave