“Critical infrastructure” once referred to things like roads, bridges and power plants. But today, the term includes the unseen digital networks that control our visible world. An easy way to protect this infrastructure from hackers is to simply keep it disconnected from the internet, but it turns out many of those systems indeed are connected to the web, unbeknownst to the people that operate them. Joining me to talk about this is Kim Zetter, senior writer for Wired. Her article, “Ten Thousand Reasons to Worry about Critical Infrastructure,” is featured on Wired.com.