Security experts say the hacker was a "state actor," and analysts have said that most of the evidence points to China.
According to Reuters, the 72 organizations hacked into included the governments of the United States, Taiwan, India, South Korea, Vietnam, and Canada, as well as international organizations such as the United Nations and the International Olympic Committee.
The Guardian states that 49 of the 72 organizations were based in the United States.
McAfee uncovered the attacks this past March, saying that the earliest attack by the hackers occurred in 2006.
McAfee's vice president of threat research Dmitri Alperovitch told Reuters, "Companies and government agencies are getting raped and pillaged every day. They are losing economic advantage and national secrets to unscrupulous competitors."
"The scale at which this is occurring is really, really frightening," Alperovitch said.
Jim Lewis, a cyber expert from the Center for Strategic and International Studies, said that much of the information obtained was of special interest to China.
One example cited was the repeated hackings of the International Olympic Committee and national Olympic Committees around the time of the 2008 Beijing Olympics.
Another was the fact that the government of Taiwan's system had been broken into; Taiwan and China have a tense political relationship.
McAfee refused to name a specific culprit; however, it pointed to a single country as responsible and called the Olympic-related hacking "particularly intriguing."
Cyber analyst Dave Clemente, from Chatham House think tank, told The Guardian that China was probably also being targeted through hacking by other countries.
"It's going in both directions, but probably not the the same extent," he said. "China has a real motivation to gain these types of industrial secrets, to make that leapfrog."
Alperovitch said that that the hacking represents a huge economic threat to companies, industries, and "entire countries that face the prospect of decreased economic growth in a suddenly more competitive landscape."
In 2009, a report released by a Canadian research group said that a cyber spy network, based mainly in China, had hacked into classified documents from government and private organizations in 103 countries, including the computers of His Holiness the Dalai Lama and Tibetan exiles.