Executives at corporate operators of critical infrastructure -- power, water, oil, telecom, finance, and transportation companies -- say that their networks face relentless attacks from cybercriminals and foreign governments, a situation that amounts to an undeclared cyberwar.

On Thursday, McAfee, a security vendor, published a cyber security report authored by the Center for Strategic and International Studies (CSIS), a public policy research group.

The report, "In the Crossfire: Critical Infrastructure in the Age of Cyberwar," is based on interviews with six hundred IT and security executives at critical infrastructure enterprises in seven industrial sectors from 14 different countries. It finds widespread worry about cybersecurity preparedness and predicts the situation will get worse.

Conducted by U.K. market research firm Vanson Bourne, Ltd., the survey suggests that cyber attacks, such as the one from China that Google recently reported, happen frequently to companies across a broad range of industries.

"More than half of the executives surveyed (54%) said they had experienced 'Large-scale denial of service attacks by high level adversary like organized crime, terrorists or nation-state (e.g. like in Estonia and Georgia),'" the report states. "The same proportion said they had been subject to 'stealthy infiltration' of their network by such a high-level adversary 'e.g. like GhostNet' -- a large-scale spy ring featuring individualized malware attacks that enabled hackers to infiltrate, control, and download large amounts of data from computer networks belonging to non-profits, government departments and international organizations in dozens of countries."

In an interview with InformationWeek, Stewart Baker, a distinguished visiting fellow at CSIS, former assistant secretary for policy at the Department of Homeland Security, and an attorney at Steptoe & Johnson, said concern about cyber attacks is real and needs to be taken seriously.

"We asked people who ought to know about attacks on their infrastructure under an assurance of anonymity and what we found is that this is a very significant threat," he said. "It really is substantial."

Baker pointed to survey findings indicating that 20% of respondents reported extortion attempts. In the U.S., U.K., and Germany, only 10% said as much. But in India, 40% reported extortion.

Survey data suggests that the average cost of a major cyber attack -- one that results in at least 24 hours of system downtime -- ranges from about $6 million to over $8 million in the oil and gas sector.

Not everyone sees cyber attacks as a source of alarm. In a recent interview with Reuters regarding the cyber attack on Google, Microsoft CEO Steve Ballmer said, "We're attacked every day from all parts of the world and I think everybody else is too. We didn't see anything out of the ordinary."

-- Nick Hoover contributed to this article.