The attack began this morning and has been focused on the U.S. East Coast, where a large number of servers are located. That hackers could take down a fundamental piece of the internet hints at the power of their capabilities.These so-called DDoS attacks work by bombarding servers with massive amounts of traffic, overwhelming their ability to reply to valid requests.Dyn and affected companies like GitHub are working to undo the damage. Companies can insulate themselves against these attacks my using multiple DNS services.While it's still too early to discern the source of the attack or infer a motive, security expert Bruce Schneier reported early last month that someone has ramping up DDoS attacks, likely probing key portions of the infrastructure of the internet for weaknesses. "We don't know who is doing this, but it feels like a large nation state," he wrote. It's unclear if those probes are related to today's attack.