According to McAfee Inc., hackers have targeted more than 70 entities over the past five years.
The firm believes it could be the largest coordinated attack ever launched.
McAfee says one of the victims was a county government in Southern California.
The types of organizations targeted indicate the attacks were likely state-sponsored, according to the firm.
"Like the World Anti-doping [Agency], that's not a target that you could attack to gain any economic benefit from it. So that's one of the points that makes us believe that it's really a state-sponsored attack," said Toralv Dirro, security strategist with McAfee.
McAfee isn't identifying which country could be behind the attacks.
The report is short on specifics, as the security firm is not naming most of the victims, nor is it stating exactly what data were stolen. Most of the victims are in the U.S. Other victims were in Canada, South Korea, Taiwan, Japan and nine other countries.
The Associated Press contributed to this report.