http referrer block

Hi.

I am runnign a site with a lot of images on it, and bandwidth stealing is a problem. I would like to implement http referrer check for every request that comes to the site. i saw someone try to implement something like this before with a module, but he was not able to get it to work right - for wxample, ttux wouldn't add last_modified headers at the time. 

what is the correct way to do this ? is there an example of "all-userspace" module that changes the processing of requests in tux (return error if some condition isn't met) ?

if i get no answer to this, i will simply put it into the main code into proto-http, with some /proc/sys/net/tux flags - i am good, but not good enough to start writing modules when i have no sample for it ...

;)

Alex