Distributed denial-of-service (DDoS) attacks are certainly nothing new. Companies have suffered the scourge since the beginning of the digital age. But DDoS seems to be finding its way back into headlines in the past six months, thanks to some high-profile targets and, experts say, two important changes in the nature of the attacks.

The targets are basically the same -- private companies and government websites. The motive is typically something like extortion or to disrupt the operations of a competing company or an unpopular government. But the ferocity and depth of the attacks have snowballed, thanks in large part to the proliferation of botnets and a shift from targeting ISP connections to aiming legitimate-looking requests at servers themselves.

In fact, said Andy Ellis, CSO of Cambridge, Mass.-based Akamai Technologies, the botnets launching many of today's DDoS attacks are so vast that those controlling them probably lost track of how many hijacked machines they control a long time ago.