Guestbook Spam

Lately I’ve been battling a new type of battle. Guestbook spam. 3 times last night I had some spammer sign my church’s guestbook promoting their Human Growth Hormone treatment and their loan service. I can’t tell if this is being done manually or by some type of bot. Each time someone signs the guestbook I get an email alerting me of the entry. Each time I have been sitting at the computer when I received notification of the entry, and corrected within minutes.
This happened with a couple of webpages I helped set up: Todd’s webpage and with Josh’s webpage. The only difference is right now both guestbooks are disabled inadvertently.
Guestbooks are SO late 90s. No one (except for spammers) uses them anymore. Instead you’ll see comments on blog entries. And now even blogs are being inundated with spam.
I use the guestbook contained on Matt’s Script Archive. I’ve been looking for a solution for this, either trying to block spam according to content (key words) or IP addresses even. However Matt’s Guestbook Script is not sophisicated enough to allow for this. (One reason I use it is because it is so easy to set up).
The internet used to be fun. It was fun when you didn’t have to repair guestbooks daily when someone tries to sell their snakeoil.
If anyone has any good solutions for guestbook spam, apart from removing the guestbook altogether, I’d love to hear it.