I do know "Gaia", which is php based, has several sorts of bot-moniters.  If you don't know how Gaia works, they give you "virtual gold" for every page you go to.  This is rife for people to abuse, obviously.  So they have bots to catch the bots, as it were.

I'm talking about seriously driven, big sites (Hustler in US, "Beate Uhse" in Germany for example) in a multi-billion business. Only the small ones are using a standard script made by amateurs (no deep knowledge about specific problems).

This industry has spend a whole lot of money to develop strategies and software.