We use the google reCAPTCHA service to verify when your lead capture form is submitted that its an actual real person and not a spammy robot. This is a free service to use which is very nice as it does a lot of magic stuff behind the scenes for you.
You can get your unique reCAPTCHA keys generated by going here.
https://www.google.com/recaptcha/intro/index.html
Click the blue 'Get reCAPTCHA' button in top corner.