The U.S. team scored the most improved in this year's NATO Locked Shields cyberwar games, but experts said that result might not be reason to celebrate.

The Locked Shields event is a "live-fire" cyberdefense exercise organized by the NATO Cooperative Cyber Defence Centre of Excellence in which teams are "tasked to maintain the services and networks of a military air base of a fictional country, which, according to the exercise scenario, will experience severe attacks on its electric power grid system, unmanned aerial vehicles, military command and control systems, critical information infrastructure components and other operational infrastructure."

During the cyberwar games, there were more than 2,500 possible attacks that could be carried out against more than 3,000 virtualized systems meant to simulate military air command and control systems, drone and ground control, a large-scale SCADA system controlling the power grid and programmable logic controllers.

Nathaniel Gleicher, head of cybersecurity strategy at Illumio and former director of cybersecurity policy for the White House, said this type of cyberwar practice is "essential to effective cybersecurity."

"Exercises like this are an important way that security teams can build experience for real threats. The Locked Shields war game is interesting in that it focuses entirely on defense: teams compete to protect their networks, with third parties playing the intruders," Gleicher told SearchSecurity. "This is an especially useful form of wargame -- defense is much more difficult than offense, and any opportunity our teams get to improve their skills in defense is a great opportunity."

John Bambenek, threat research manager at Fidelis Cybersecurity, said it was especially important for the cyberwar games to be "live-fire."

"Defenders learn best in a live-fire environment. When the 'red team' can simulate what adversarial nations are doing, that's even better," Bambenek told SearchSecurity. "Tabletop exercises can only take learning so far. Operators need valuable experience, and they need to do so under fire."