Squiggly-letter test used to tell humans, computers apart getting harder as machines catch on

Tell me if this sounds familiar: you’re online, ready to buy some concert tickets or to sign up for a new email account. But before you’re allowed to
proceed, you have to prove you’re a human being by deciphering a mess of distorted, squiggly letters and numbers, then typing them into a text box.
This is what’s called a Captcha, or completely automated public Turing test to tell computers and humans apart.

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