By the year 2000, the internet was already becoming a cesspool. The bad guys used software bots to sign up for millions of fake email accounts—for sending out spam.

PhD student Luis Von Ahn stopped them. He invented the CAPTCHA, that website login test where you have to decipher the distorted image of a word. Or you have to find the traffic lights or fire hydrants in a grid of nine blurry photos.

Those tests help to keep down the volume of spam, spyware, and misinformation; they advance the clarity of digitized books and the intelligence of self-driving cars; and, by the way, they made a handsome profit.

The only problem: We HATE those tests!

Guest: Luis Von Ahn, co-inventor of CAPTCHA, co-inventor and CEO of Duolingo.

Learn more about your ad choices. Visit megaphone.fm/adchoices