Referer Spam (Referrer Spam) is a form of spam that few will be concerned with unless they have a web site or blog. It involves making hits on a site with fake referers to gain a line entry in the servers log file. This then becomes a part of the data generated by the log analyzer such as AWStats.
Now you say big deal what did that do for the spammer creep? Nothing if you don’t give the world access to your analytics data like so many hapless webmasters do. When the search engines pick it up it looks like your are giving a link to the spammer and gives them a chance at more Page Rank.
Here is a better explanation of Referer Spam and solutions you can use to make it a waste of their time. In a nutshell password protect your log analysis, and don’t click their links in your stats giving them traffic.
Here is the main point from Jotsheet:
Best practice #1: Donâ€™t publish your referrers
If bloggers (and other website maintainers) did not publish this information, spammers would not bother to send these spoofed requests to blogsâ€”it would be pointless. (For a humorous example, check out a blog entry on this very subject thatâ€™s actually being targeted by pr0n site referral spammers.) Therefore, I propose that bloggers discontinue this practice. Others agree. I, for one, have never clicked on a link published in a blogâ€™s â€œSites referring to meâ€? (or similar) section. I think many bloggers simply believe this is a neat feature and have not evaluated its detrimental effect on the blogosphere as a whole.