The Chinese government on Thursday disputed a report labeling it the world's most aggressive offender in probing for holes in other nations' Internet security and encouraging a looming global cyber showdown.

The report, issued Thursday by Santa Clara-based security software vendor McAfee Inc., said government-affiliated hackers in China are at the forefront of a brewing "cyber Cold War" still in its infancy.

"China has also been attacked by hackers of some countries, so the Chinese government attaches great importance to and participates in the international law enforcement cooperation in this area," Foreign Ministry spokesman Liu Jianchao said at a briefing Thursday.

Liu refused to reveal which countries were targeting China.

• Click here to download the 40-page McAfee report (pdf, free registration required).

Within two decades, according to McAfee, the scuffle could erupt into a worldwide conflict involving hundreds of countries attacking one another's online networks with sophisticated software.

McAfee said about 120 countries are developing cyber attack strategies and most are merely testing them to determine the risks involved in certain tactics — though devastating international attacks could come one day.

Based on McAfee research and input from security experts with NATO, the FBI and other intelligence outfits, the report said hackers in China are believed responsible for four out of five major cyber attacks on government targets in 2007.

• Click here to visit FOXNews.com's Cybersecurity Center.

The biggest intrusions appear to have targeted a Pentagon computer network and government agencies in Germany, India and Australia and New Zealand.

"The Chinese have publicly stated that they are pursuing activities in cyber espionage ... they speak of technology being a large part of war in the future," the McAfee report read.

McAfee said that in 2007, there were more attacks reported on critical national infrastructure than ever before.

Targets included financial markets, utilities and air traffic control machinery, and the attacks were believed to have been launched by governments or government-allied groups.

Another large attack occurred in April, when severe and well coordinated cyber attacks struck Estonia's banks, government institutions and media outlets.

Estonian officials have claimed the attacks originated in Russia. Russian authorities have denied any involvement.

China has steadfastly denied it is engaged in any cyber crime and said its networks too have been targeted.

The McAfee report also detailed the growing threat to Web surfers from increasingly sophisticated techniques to steal personal information online and install malicious code on victims' computers to herd them into networks of compromised machines that pump out spam or fire off attacks.

The report also examined the market for newly discovered — and unpatched — software flaws. The existence of that market has blurred the line between legal and illegal sales.