Latest in Anti Spam

Tutorials, tips, and howtos about prevent email spam (unsolicited bulk email), both end users and administrators of email server use various anti-spam techniques under Unix / Linux operating systems.

I own a small business website. However, bots started to abusing my forms such as contact.php. How do I stop bots bots from abusing my site? How do I tell if PHP form is submitted by a person or a script?