If your webhost allow the use of .htaccess, there are several options to stop trackback spam from occuring in the first place.
So If the refferer contains the word, it will be blocked. This strategy will block many sites, for example the viagra one will block stuff like:
www.buy-viagra.com but also stealth domains like
www.7zulu.com/viagra.html etc. etc.
You can stop it via the .htaccess file
PHP Code:
# Single word blocks
RewriteEngine On
RewriteCond %{HTTP_REFERER} poker [OR]
RewriteCond %{HTTP_REFERER} medicine [NC,OR]
RewriteCond %{HTTP_REFERER} pills [NC,OR]
RewriteCond %{HTTP_REFERER} diet [NC,OR]
RewriteCond %{HTTP_REFERER} viagra [NC,OR]
RewriteCond %{HTTP_REFERER} mortgage [NC,OR]
RewriteCond %{HTTP_REFERER} casino [NC,OR]
RewriteCond %{HTTP_REFERER} insurance [NC,OR]
RewriteCond %{HTTP_REFERER} loan [NC,OR]
RewriteCond %{HTTP_REFERER} buy [NC,OR]
RewriteCond %{HTTP_REFERER} xanax [NC,OR]
RewriteCond %{HTTP_REFERER} meridia [NC,OR]
RewriteCond %{HTTP_REFERER} incest [NC,OR]
RewriteCond %{HTTP_REFERER} lesbian [NC,OR]
RewriteCond %{HTTP_REFERER} viagra [NC,OR]
RewriteCond %{HTTP_REFERER} adult [NC,OR]
RewriteCond %{HTTP_REFERER} hentai [NC,OR]
RewriteCond %{HTTP_REFERER} tramadol [NC,OR]
RewriteCond %{HTTP_REFERER} phentermine [NC,OR]
RewriteCond %{HTTP_REFERER} gambling [NC,OR]
RewriteCond %{HTTP_REFERER} texas- [NC,OR]
RewriteCond %{HTTP_REFERER} holdem [NC,OR]
RewriteCond %{HTTP_REFERER} pharmacy [NC,OR]
RewriteCond %{HTTP_REFERER} ultram [NC,OR]
RewriteCond %{HTTP_REFERER} tramadol [NC]
RewriteRule .* - [F,L]
Just add the above to your .htaccess file, Feel free to add others
heres another under used trick if your using a .htaccess file
If you pay for your bandwidth, this little line could save you hard cash.
PHP Code:
<ifModule mod_php4.c>
php_value zlib.output_compression 16386
</ifModule>
All it does is enables PHP's built-in transparent zlib compression. This will half your bandwidth usage in one stroke, more than that, in fact. Of course it only works with data being output by the PHP module, but if you design your pages with this in mind, you can use php echo statements, or better yet, php "includes" for your plain html output and just compress everything!
Enjoy