Last month, the world narrowly avoided a cyberattack of stunning ambition. The targets were some of the most important computers on the planet. Computers that power the internet. Computers used by banks and airlines and even the military.

What these computers had in common was that they all relied on open source software.

A strange fact about modern life is that most of the computers responsible for it are running open source software. That is, software mostly written by unpaid, sometimes even anonymous volunteers. Some crucial open source programs are managed by just a single overworked programmer. And as the world learned last month, these programs can become attractive targets for hackers.

In this case, the hackers had infiltrated a popular open source program called XZ. Slowly, over the course of two years, they transformed XZ into a secret backdoor. And if they hadn't been caught, they could have taken control of large swaths of the internet.

On today's show, we get the story behind the XZ hack and what made it possible. How the hackers took advantage of the strange way we make modern software. And what that tells us about the economics of one of the most important industries in the world.

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