Referer Spam

Referer Spam is a kind of search engine -targeted spam . The technique involves making repeated web site requests using a fake referer url pointing to a spam-advertised site. Sites that publicize their referer statistics will then also link to the spammer's site. This benefits the spammer because of the free link, and also gives the spammer's site improved search engine link placement due to link-counting algorithms that search engines use.

As with email spam, web site operators who receive unwanted referer spam may respond using filtering.

An example configuration fragment for filtering using the Apache server is as follows:

 RewriteEngine On
 #a known spamming site
 RewriteCond %{HTTP_REFERER} ^http://(.*\.)?egolddomain.(com|net)(/.*)?$ [NC,OR]
 #various "porno" words when separated by line breaks are probably spam
 RewriteCond %{HTTP_REFERER} ^http://.*(\b)porn(o(graph(y|er))?)?(\b).* [NC,OR]
 #referer url's with excessive - characters are probably spammers
 RewriteCond %{HTTP_REFERER} ^(http://www.)[a-z]+-[a-z]+- [NC,OR]
 #can add as many rules as desired following the pattern of the previous line
 #set an environment variable "BAD_GUY" so we can send their logs to a different file
 RewriteRule ^(.*) %{HTTP_REFERER} [R=301,E=BAD_GUY:1,L]
 #because we have set E=BAD_GUY above, we can do this in our log file:
 CustomLog /var/log/apache/access.log combined env=!BAD_GUY
 CustomLog /var/log/apache/access_bad.log combined env=BAD_GUY

The "fake" web site hits will go to access_bad.log, whereas normal traffic goes to access.log. The "RewriteCond" lines contain Regular expressions that can be used to match any undesirable traffic, thereby excluding it.

See also

• Protect Your Site From Log File Spammers

Retrieved from http://en.wikipedia.org/wiki/Referer_spam

Reprinted from Wikipedia, The Free-Content Encyclopedia under the GNU Free Documentation License.

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February 04 2012 04:08 UTC