||This article possibly contains original research. (July 2010)|
Referrer spam (also known as log spam or referrer bombing) is a kind of spamdexing (spamming aimed at search engines). The technique involves making repeated web site requests using a fake referer URL to the site the spammer wishes to advertise. Sites that publish their access logs, including referer statistics, will then inadvertently link back to the spammer's site. These links will be indexed by search engines as they crawl the access logs.
This benefits the spammer because the free link improves the spammer site's search engine ranking owing to link-counting algorithms that search engines use.
As with e-mail spam, referrer spam may be filtered or blocked. A website operator may mitigate referrer spam by preventing search engine spiders from crawling the site logs by moving them to a non-public area such as a password-protected area, by using a robot exclusion file, or by appending the nofollow value to the links.
It is found that not all referrer spams limit to pollute GA stats but some of these actually hit the web server. It is suggested that filtering referrer spam may only hide it from the Google Analytics report but can continues to consume server bandwidth. To save server bandwidth these spams should be blocked using .htaccess file.
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- www.codegolem.com Technical article about implementing an Anti-Referrer-Spam Module in ASP.NET/C#
- Using .htaccess to block referrer spam Technical Article about how to block referrer spam with Htaccess
- Semalt, Darodar and other Referrer Spam Explained - Technical overview of referrer spam in Google Analytics: how it happens and what you can do