A cold cyberwar is already under way, and some experts predict it will get hot this year — with real deaths.

"Nation-state attackers will target critical infrastructure networks such as power grids at unprecedented scale in 2013," warns Chiranjeev Bordoloi, CEO of security company Top Patch, according to CNNMoney. "These types of attacks could grow more sophisticated, and the slippery slope could lead to the loss of human life."

The world's top military powers are either developing or already have cyberwar programs. Iran is typically cited as the most likely to launch a cyberattack, but China and Russia also have sophisticated cyber capabilities.

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Last year, an attack against oil company Saudi Aramco crashed 30,000 computers and a concerted attack shut down websites of several of the largest U.S. banks, CNNMoney reported.

The U.S. financial system and infrastructure, including the stock market, electrical grid and water purification system, could be targeted. Defense Secretary Leon Panetta has said the United States might use military force against a nation launching a cyberattack.

The frequency of cyberattacks between nations will increase, predicts online security firm McAfee in a new report.

The next step might be a combination of a cyber and physical attack, McAfee warns. "If a group can remotely disrupt a critical infrastructure, such as a defense or communications system, a conventional attack could more easily cause more damage."

Although not predicting such an attack this year, the experts caution that their fears of one "are not just fantasy."

In addition, criminals and “hacktivists” will use increasingly sophisticated actions, with a wide assortment of malicious programs. Typically, cybercrooks usually want financial gain or to steal intellectual property, but McAfee predicts more attacks that simply want to cause as much damage as possible.

"The worrying fact is that companies appear to be rather vulnerable to such attacks."

Video: Economist Predicts 'Unthinkable' for 2013