In the Hitchhiker’s Guide to the Galaxy, Douglas Adams wrote about a device called an electronic thumb. Electronic thumbs were used by hitchhikers to flag down passing spaceships and help them get on board. Since not all spaceship captains were inclined to give hitchhikers lifts, some engineers spent all their time creating new devices to protected against electronic thumbs. This lead to the engineers creating electronic thumbs that could defeat these new devices, leading to even more anti-thumb devices, leading to better electronic thumbs, leadi…. you get the idea.

The people who create CAPTCHAs and the programmers who work for the spammers are locked in a similar epic battle.

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