The Berkman Center dug up media reports of 140 DDoS attacks against more than 280 different human rights and dissident sites in the 12 months between September 2009 and August 2010, likely only a fraction of the actual numbers, said Zuckerman, as many go unreported.

Zuckerman's team also polled more than 300 human rights and independent media sites around the world, and convinced 45, or 14% of the total, to talk about DDoS attacks.

Of the groups that responded, almost two-thirds (62%) had been hit with a DDoS attack in the last year, while slightly fewer (61%) said that their sites had experienced unexplained downtime for their domains.

According to the Berkman Center, there was a "particularly high prevalence" of attacks against sites in Burma, China, Egypt, Israel, Iran, Mexico, Russia, Tunisia, the U.S. and Vietnam, with groups targeted both from within their own borders and from outside their countries.

The center's report highlighted multiple, sustained DDoS attacks against Novaya Gazeta, Russia's most liberal independent newspaper; attacks aimed at a Vietnamese organization protesting bauxite mining in that country; ones launched by the so-called against the Iranian government opposition site mowjcamp.com; and others conducted by a hacker who calls himself "Jester" against sites he said promoted Islamic Jihad.