How do I catch the email address of a spammer?

I know that I can check IP addresses and domains against blacklists like Spam开发者_JAVA百科haus and co, but is there a way that I can prevent iamaspammer@gmail.com from signing up at my website?

most form spam is created with fake/invalid email adresses which are only used once, so creating a blacklist is pretty useless.

it's way more effective to block known bot IPs and malicious URLs in the form body.

I also suggest securing your form with a good captcha.

If you don't want to bother your users with captchas, there is a less obtrusive, but also less effective trick: create a additional form field and hide it via css. only accept the form if this field was submitted empty. many bots usually fill out all fields, so you can reject the form if this hidden field has any content.