Ref to the robots

hello all ,
we prevent from robots by creating a robot.txt file in the server to prevent these robots , as you know these kind of robots abuse our text fields and etc and put unwanted data in our bank , for example i have comment part in my website and i did not respect to security matters like CAPTCHA so my sql database filled with unwanted data .
or there are some robots that they busy a website so the website will be down .
now i want to know how to find and execute these robots on my website ?
thanks

This really belongs in the security section not the database section.

But you have several options open to you, hidden fields that dont get fillled in (bots always fill every field), monitor the time between form loading and submission (most bots are much faster than humans), make sure that the submission actually comes from the your site (once a bot has found your form it usually just posts the spam directly), captcha and image verification work well, as do color verifications.

Robot.txt isnt going to help in fighting span as these bots dont even look at the file.

thank you mandes .
but my meaning is how to create a robot and work with it ?

Why do you want to write a robot script ?

yes , how can i find out it ?