INTERNET BOTS..

• Several companies (Yahoo!, Microsoft, etc.) offer free email services. Few years ago, most of these services suffered from a specific type of attack: "bots" that would sign up for thousands of email accounts every minute 

• The solution to this problem was to use CAPTCHAs to ensure that only humans obtain free accounts. In general, free services should be protected with a CAPTCHA in order to prevent abuse by automated programs