Auto Delete Spam Comments?

Hi,
I’ve been getting a huge amount of spam comments lately on my site and to be frank it’s #$#$ the $#$# out of me. Since the IP changes it appears that any method of banning an IP (does this exist in WordPress) would be fruitless.
The method that would appear to work is any function that says “If there’s more than 1 hyperlink in a comment – it’s TOAST”. Does such a plugin or hack exist? I’m getting sick of going through 75 comments and clicking delete on each when I’d prefer them to automatically delete.
Thanks for any info.
Reid