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. Help support Planet Money and hear our bonus episodes by subscribing to Planet Money+ in Apple Podcasts or at plus.npr.org/planetmoney. Learn more about sponsor message choices: podcastchoices.com/adchoices NPR Privacy Policy

Karen McDonough of Quincy, Mass., was enjoying her tea one morning in the dining room when she saw something odd outside her window: a group of people gathering on her lawn. A man with a clipboard told her that her home no longer belonged to her. It didn't matter that she'd been paying her mortgage for 17 years and was current on it. She was a nurse with a good job and had raised her kids there. But this was a foreclosure sale, and she was going to lose her house. McDonough had fallen victim to what's called a zombie second mortgage. Homeowners think these loans are long dead. But then the loans come back to life because they get bought up, sometimes for pennies on the dollar, by debt collectors that then move to collect and foreclose on people's homes. On today's episode: An NPR investigation reveals the practice to be widespread. Also, what are zombie mortgages? Is all this legal? And is there any way for homeowners to fight the zombies? You can read more about zombie second mortgages online at: npr.org/zombie Correction: An earlier version of this episode description misspelled Karen McDonough's last name as MacDonough. Help support Planet Money and get bonus episodes by subscribing to Planet Money+ in Apple Podcasts or at plus.npr.org/planetmoney. Learn more about sponsor message choices: podcastchoices.com/adchoices NPR Privacy Policy