building a basic human test with php

Question

Im making a rudimentary "human test" for a form on my website.

I want to take the current date (to the minute, not second), and combine that with the users REMOTE_ADDR, then from that generate a string (perhaps use md5?) then limit that to 6 characters.

This code will then be presented to the user, which is instructed to copy it to a particular text box, upon submission will be verified and allow the form to process.

I dont know if there is an easier way to do this, but this is something i think will work for me and be a quick fix. Any suggestions?

Answer 1

Generate an MD5 from any source (inc. totally random). Put it on the screen and store it in the session. Check it. Voila.

Using a captcha library is, obv. much more secure though. There's plenty of very good and very very easy to install ones about.

Answer 2

I dont know if there is an easier way to do this, but this is something i think will work for me and be a quick fix. Any suggestions?

If you just need a quick fix, try for something simpler. I had a very popular website with a notoriously effective Turing Test:

Check this box if you're a human: [ ]

This little fix brought my spam count down from 10s of 1000s of messages everyday to 1 or 2 every few months. Of course, once the bots wised up, I had to make my test much more difficult:

What's the sound a cat makes? (Rhymes with 'cow') [________________]

Never had anymore problems after that. YMMV.

Answer 3

I would say the simplest solution would be to use a honeypot. Basically, create a hidden field called Name or something of that sort, and then check to see if the field has data upon submission. If it does, you know it is a bot! Since it is hidden, human's will not be able to populate that field, only bots will!