Yes how DOES a bot manage the capcha thing especially if it's a tricky one to decipher?
You know, i'm not sure about that one

Even I can't get past some of them
When I helped moderate another gardening forum, we could identify the point of origin and the IP of the spammer. Then the webmaster could ban the little twerp. I once offered to go to India and bang someone's head against a table, but the webmaster wouldn't spring for round-trip airfare. He did offer me a one-way prepaid ticket.
Webmaster on the other forum had threats from a couple of trolls a while back, they were making it personal and threatening his business too.
He used their email to back track them to the forum they were planning the attack from, joined it under a false name, found selfies of both of them and then pasted them onto the gardening forum.
The effect was brilliant, back on their forum they were trying to work out how he got pics of them
A little more digging came up with their real names and addresses, he went round to one of the houses with a couple of big lads, the troll refused to come out, hiding behind his mummy
Attacks stopped after that
