An official with Brazil’s electricity regulator has confirmed that large scale blackouts in 2005 and 2007 were caused by people hacking into the computers that control the electricity grid.The official with ANEEL, which regulates electricity producers and transmission in Brazil, said that while the evidence was not absolute, it was widely believed that hackers broke into control computers and shut down power to millions.
http://www.abc.net.au/news/stories/2009/11/08/2736567.htm