Public caught in the crossfire

"If a major cyber conflict between nation states were to erupt, it is very likely that the private sector would get caught in the crossfire," it said.

"Most experts agree that critical infrastructure systems ? such as the electrical grid, banking and finance, and oil and gas sectors ? are vulnerable to cyber-attack in many countries," it said.

"In most developed countries, critical infrastructure is connected to the internet and lacks proper security functions, leaving these installations vulnerable to attacks," McAfee said.

It said some nation states "are actively doing reconnaissance to identify specific vulnerabilities" and quoted one unidentified expert as saying they were "laying the electronic battlefield and preparing to use it".

Rules of engagement not clear

McAfee said what constitutes an act of war in cyber space ? and the proper response ? was not yet clear.

"Cyber warfare entangles so many different actors in so many different ways that the rules of engagement are not clearly defined," it said.

"Without a proper definition in place, it is nearly impossible to determine when a political response or threat of military action is warranted," it said.

The McAfee report was prepared by cyber security expert Paul Kurtz, a former White House adviser and included interviews with more than 20 international relations, national security and internet security experts from around the world.