captcha, eli5
a service provider has detected unusual traffic, so he builds a wall between usa and mexico. now nobody can pass the border.
to allow some traffic, service provider builds small gate with border control, where everyone needs to scan their face and play games to verify they are humans (ants cannot pass)
result:
90 % of visitors turn around because passing border is made so difficult, so the traffic problem is solved already
5 % of visitors scan their face and play games to pass the border
5 % of visitors are developers who automate the game by building robots that fake face scanning and can play the games
a service provider has detected unusual traffic, so he builds a wall between usa and mexico. now nobody can pass the border.
to allow some traffic, service provider builds small gate with border control, where everyone needs to scan their face and play games to verify they are humans (ants cannot pass)
result:
90 % of visitors turn around because passing border is made so difficult, so the traffic problem is solved already
5 % of visitors scan their face and play games to pass the border
5 % of visitors are developers who automate the game by building robots that fake face scanning and can play the games