A typical CAPTCHA security check asks users to read distorted text made difficult for spammers to solve.
A typical CAPTCHA security check asks users to read distorted text made difficult for spammers to solve.
A typical CAPTCHA security check asks users to read distorted text made difficult for spammers to solve.

As Web sites' 'CAPTCHAs' get harder, visitors leave discouraged

June 18, 2012 12:00 AM