The US has apparently been hit with massive denial of service attacks recently, according to an article republished in Revolution News. Denial of service attacks (referred to as DDoS in the article) are when a group of people, or someone who has control over numerous computers or networks, floods a web site or server and causes it to crash or work very slowly because it can't handle the traffic.
I was interested by this map, where such attacks are tracked. If you move your cursor over the map, a window pops up explaining the different attacks. The article says the map hasn't been being updated regularly since the latest attacks started.