How to stop bots and spams from submitting comments?

Question

Currently

1. I am using captcha image
2. I created text field and hide it using javascript. i want its value to be empty on server side, because bots are supposed to fill all the fields on the form. if value isn't empty it it does not process comment.
3. I also use timestamps to check how long it took while submitting the comment. I supposed if the comment was submitted within 15 seconds, it comes from bot so i also stop processing the comment.

But still I couldn't control bots to submit my comments form. Please help what should I do now?

Answer 1

Add a hidden field with a misleading id / name

<input type="hidden" id="Username" name="Username" value=""/>

If a bot comes along and fills out your form, they are likely to fill in the hidden field, which users should not be able to, so just disallow the submission if the hidden field has data.

Answer 2

Why not implement Akismet and let them handle it for you? They have a well documented API, and thousands of people rely on it for spam prevention on Wordpress blogs. I haven't seen a spam comment in probably 3 years now using Akismet on my wife's blog.