The attack brought down several major American and South Korean Web sites at least temporarily. But other South Korean officials expressed doubt that the North Koreans could carry out such an attack.

Keith Epstein, an investigative reporter for BusinessWeek whose specialty is cyber security, joins Martin Savidge to discuss who is behind the cyber attacks, the consequences of the attacks and how the U.S. can improve cyber security.

The network, called Ghostnet, is based mainly in China. Among the computers it targeted were those of Tibet’s spiritual leader, the Dalai Lama, and Tibet’s government-in-exile in India. Scholars say the operation may have helped identify people in Tibet who talk to exiled Tibetans, putting those in Tibet at risk of reprisals from the Chinese government, which controls Tibet.

The Canadian researchers said the spying activity they found was just the tip of the iceberg.

Keith Epstein, an investigative reporter in BusinessWeek’s Washington D.C. bureau who specializes in cyber security, joins Martin Savidge to discuss Chinese cyber spying, what information is at risk and defense systems.