We learned this week that a hacker tried to poison the water supply in a town outside Tampa, Florida. An operator at the plant noticed the intrusion, and there was no significant damage done to the city’s water supply. But the thing is, a lot of our critical infrastructure is connected to the internet, and not all of it is very secure. Molly speaks with Nicole Perlroth, who covers cybersecurity for The New York Times and is the author of the new book “This Is How They Tell Me the World Ends: The Cyberweapons Arms Race.” She asked her how we could start to tighten things up.