Msg#: 14362 posted 5:20 pm on May 31, 2006 (gmt 0)
Very good question. I have a lot of user-generated content on my sites, and there are some rewards for those who have their content viewed the most, so we do occasionally find traffic from traffic exchanges and such. (Despite this being prohibited from our TOS policy.)
We constantly manually review all referrals that come from sources other than the major SE's. It is time consuming, but I don't know of another way and I think it is worth it.
Look at the referrer field, that's the most important. I don't do this every day, but I certainly take a look if traffic is notably higher/lower than expectations.
argv1900: You can ban referrals from any website via the .htaccess file, using the HTTP_REFERER field. I've only ever heard of people actually doing this in order to prevent the hotlinking of images, but in theory you can also prevent surfers from any website from accessing your regular pages.