Recently, I’ve had a very big problem with the guestbook I have on my personal website: it was flooded with spam. I think I was deleting several hundreds messages each day, and they kept on appearing.
I was desperate, I was even thinking of deleting my guestbook. Although it had a captcha in place, it seemed not to be stopping those messages at all. Probably there are programs which can read those captchas, so they are semi-useless.
Before deleting the guestbook, however, I looked through the files on my server and I noticed one that was not mine. It was called postinfo.html and it seemed to be something that granted access to external users to post content on my site’s pages. I deleted it, and the messages seemed to slow down a bit. Then I changed the permalink to my guestbook and I added an instruction on robots.txt to disallow all bots from crawling that page.
It worked. I don’t know for how long, but I’ll keep you posted.