Use something in URL not usual

Greetings,
I had the trackback module installed for some time, but I had to unistall it cause I've been spammed from anonym proxy server bot: the problem for this bot is that they run a script that send a lot of trackback spam every day and it's really impossible, even if they're in queue approval list to delete them, to administrate anyway.
For this reason I ask if it's possible to have a system that can verify the trackback sender and accept it anyway only when you got another answer from the sender. If this is not possible all i ask is to have not a simple url to trackback that is not so always the same as www.sitename/node/trackback/200/ can be for evey node, but at least something like www.sitename/node/trackback/6352.200/ where 6352 is a random number for node 200 .
Thanks a lot