A year ago, a DDoS attack caused internet outages around the US by targeting the internet-infrastructure company Dyn, which provides Domain Name System services to look up web servers. Monday saw a nationwide series of outages as well, but with a more pedestrian cause: a misconfiguration at Level 3, an internet backbone company—and enterprise ISP—that underpins other big networks. Network analysts say that the misconfiguration was a routing issue that created a ripple effect, causing problems for companies like Comcast, Spectrum, Verizon, Cox, and RCN across the country.