March 13, 2014: The head of Israel's military intelligence recently called cyber warfare the biggest revolution in warfare, more than gunpowder and the utilization of air power in the past century. The most formidable nations on Earth currently have militaries - as well as power grids, nuclear arsenals, commercial flight systems and countless other vital entities - that are wholly dependent on computers. Defending them - and attacking those of other countries - is major business, a major part of national security strategies and a major fear of anyone who understands the vulnerabilities of their own country's machines. The best-equipped nations have enormous cyber defense - and offense - departments.

Here are the top dogs of global cyber warfare.

#4: United States of America. The U.S. has an enormous cyber-intelligence apparatus that is widely considered to be tied for the fourth most powerful in the world. America's greatest strength lies in its ability to collect and retain colossal amounts of digital data regarding the abilities of other countries - often gleaned in a fashion that has come under recent global scrutiny.

#3: Russia. Russia is widely believed to have a massive state-sponsored cyber warfare program that infiltrates the official apparatuses of foreign countries as well as domestic "enemies." Russian cyber attacks target economic, military and commercial entities of nations across the world, including the United States. Several Russian defectors outlined Russian misinformation campaigns, as well as infiltrations into private companies that service the U.S. government and military.

#2: Israel. Outspoken in its assertion that the country is the target of constant cyber attacks, Israel has established its own "cyber gym" to train hackers in defending the Jewish state's digital networks. But Israel doesn't only play defense. It is widely believed to have sabotaged the heart of Iran's controversial nuclear program, its uranium enrichment center, with the notorious Stuxnet virus in 2010.

#1: China. Although it is next to impossible to determine how much is the work of private companies or individuals, and how much is state sponsored, experts point to China as the undisputed leader in global cyber warfare. China is believed to have hacked the Australian intelligence apparatus, Indian government networks and departments within the Canadian government. The U.S. suspects China of both sabotage and espionage of American defense networks, private corporations, industrial organizations, research facilities and industrial assets. Congressional panels have called China the greatest existing threat to America's digital security.

Defending against cyber attacks is a top priority for the most sophisticated nations. Whether it's espionage, sabotage, investigative strikes, menacing or simply creating a culture that allows their best private hackers to target sovereign nations, the most powerful countries in the world all realize the power of cyber warfare. With water supplies, air traffic, power grids and countless other vital infrastructure relying on computers, cyber warriors spare no expense building their capabilities to both attack and defend. -- Andrew Lisa