We have experienced some instability on our server lately. Checking log/messages there is a lot of messages like this
Apr 25 20:27:17 lillevinkel2 drupal: http://skobloggen.lillevinkelsko.no|1335378437|page not found|18.104.22.168|http://skobloggen.lillevinkelsko.no/http://www.magicptp.com/promote.php?id=dongxh|http://pulsreklamy.pl/|0||promote.php
They are from a lot of different ip adresses. I added in .htaccess that everything with http in should be denied. pasting the url from the log results in access denied in browser, but the log is still filling with this. What can I do to prevent this kind of spidering or stop the requests before they result in a page not found?