Earlier this month, the hacker collective Anonymous made headlines with two high-profile attacks on North Korea. In addition to leaking membership records from Uriminzokkiri, the official North Korean news website, Anonymous shut down several state-run websites using distributed-denial-of-service, or DDoS, attacks.
In a DDoS attack, several computers send so many requests to a single Web server that it overloads, slowing or even completely shutting down the hosted websites. After open source software distributor VideoLAN experienced a DDoS attack, developer Ludovic Fauvet used Logstalgia to create a video visualization of what a DDoS attack looks like.
As a form of comparison, here's a Logstalgia visualization of normal server activity. Notice how this looks more like a psychedelic game of Pong, rather than a full-on onslaught.