What is a bot trap?

[fischermx]

I've read that term in several places here, but no one explain exactly what it is or how does it work?
I understand a rap trap :), but could you trap a bot?

[goodroi]

It is a way to identify bad bots that do not honor robots.txt and then block the ip addresses they come from.

#1 - Create an empty subdirectory
#2 - Block this subdirectory with your robots.txt
#3 - Place a 1 pixel link in that directory (humans wont see it, only bots will follow it)
#4 - Track all ip addresses that hit that link and then block those ips from accessing your site

This system will identify the bots (more specifically their ip addresses) and will hopefully avoid accidentally blocking the ip addresses of human visitors.