I've written about referer spam before and sadly things haven't changed much. My site, as do many others, still gets hit on regular basis by referer spam bots in their never-ending quest to increase google ranking. Unfortunately, bandwidth is cheap and they don't appear to care that hitting my site is not going to help them - google does not index my statistics pages, so appearing there doesn't help anyone get a better pagerank.

I use mod_rewrite and what is now a forest of rules to deny them http access.
Worst offenders by far:

RewriteCond %{HTTP_REFERER} allinternal\.biz [OR]
RewriteCond %{HTTP_REFERER} djhits\.com [OR]
RewriteCond %{HTTP_REFERER} ass-traffic\.biz [OR]
RewriteCond %{HTTP_REFERER} drtushy\.biz [OR]
RewriteCond %{HTTP_REFERER} asstraffic\.biz
RewriteRule .* - [F,L]

Helpfully, this particular bot comes from one IP. Thanks guys, that's very thoughtful of you..

iptables -A INPUT -p tcp -s 69.31.79.2 -j REJECT

Of course, my iptables are full of these entries from flood-comment spammers already.. Most of these are proxies, but many appear to be hijacked machines on dsl and cable connections. People without firewalls suck.

212.21.228.22
adsl-68-122-118-202.dsl.pltn13.pacbell.net
233-cust-102.venturenet.net
82-41-114-38.cable.ubr05.dund.blueyonder.co.uk
195.38.93.230
mail.tsp-diffusion.com
160.80.2.236
200.222.12.98
c414-2.impsat.com.co
81.192.204.166
208.60.60.3
24-117-149-192.cpe.cableone.net
80.58.33.172.proxycache.rima-tde.net
sys53.3fn.net
i-195-137-51-66.freedom2surf.net
200.223.11.155
pi15.krosno.sdi.tpnet.pl
mikrotik-noc-eth0.antelecom.net
210.95.104.2
206-10.istrength.net
208.32.128.15
210.8.211.138
host83-54.pool81113.interbusiness.it
alfaproxy.pai.net.pl
mail2.westsiderc.org
216.94.87.66
ddsl-216-68-163-214.fuse.net
eul0600086-pip.eu.verio.net
alfaproxy.pai.net.pl
srv.vibehosting.com