Targets for the intrusions in a five-year campaign covered 72 major organisations around the world, including the governments of India, US, South Korea, Vietnam, ASEAN, IOC and the world anti-doping agency, The Washington Post reported, quoting a McAfee report.
The networks breached included UN secretariat in Geneva, a US Energy Department lab and 12 major US defence firms engaged in top secret futuristic weapons system, the report said.
"The cyber snooping appears to have been going on for several years," the report said, tracing the hacking to at least one "state actor" behind the attack, but declined to name it, though the security experts said the evidence pointed to China.
"We were taken aback by the audacity of the perpetrators," McAfee vice president Dmitri Alperovitch said in a 14-page sensational report released today.
"What is happening to all this data...is still largely an open question. However, if even a fraction of it is used to build better competing products or beat competitors at key negotiations, the loss will represent a massive economic threat," he said.
Alperovitch said McAfee had notified all the 72 victims of the cyber attacks, which were now under investigations by law enforcement agencies around the world.
He declined to give the names of the departments of the governments hacked or give more details of the companies infiltrated.
"This is the biggest transfer of intellectual property in history and the scale at which this is occurring is really frightening," the McAfee official said.
McAfee said that it had come across the extent of hacking in May and had dubbed the uncovering of the plot as ''Operation Shady RAT''.
The company said its researchers discovered logs of the attack while reviewing the contents of a "command and control server" as part of its investigations into security breaches of defence companies.
Intruders, according to McAfee report, sought data on US military system and satellite communication, among other prizes.