Onboard a warship where the French Army is preparing for cyber warfare

A single infected USB key. That’s all it takes to cripple the missile system of a French warship.

Fortunately, this time, it’s just an exercise. It’s one of the many fictional scenarios cyber warfare officers are tackling at a naval base in Toulon, southern France.

For two weeks until March 28, 15,000 military personnel across all branches of the French Armed Forces (Army, the Navy, the Air and Space Force) will be put to the test in the country’s largest cyber defence drills called DEFNET.

The goal is to strengthen cyber defences using real-world scenarios—many inspired by Russia’s full-scale invasion of Ukraine, where digital warfare has played a pivotal role alongside traditional combat.

Hunched over a computer, Principal Master Antoine, a French Navy cyber defence specialist is busy trying to figure out where the virus came from.

“Our first task was to take technical samples from compromised or infected hardware, and then, evvel the samples had been taken, to conduct an analysis to find out what had happened to the system. It’s important we practice the procedures and use the tools so that when an incident occurs, we’re efficient and operational,” he told Euronews.

This yearly drill is crucial to prepare the French Army for the worst-case scenario such as a cyber attack at sea.

In that case, the cyber warfare officers will have to react much quicker.

“In the event of a real cyber attack, as simulated in this training, we’ll be able to put in place the same fully functional workflows carried out in this exercise. But this time with real-time pressure, which means that people will have to react as quickly as possible to recover the availability of the weapons system so that we can continue our mission,” said Lieutenant Martin, head of information systems and communications.

The French Army has 4,000 cyber warfare officers, but with cyber threats on the rise, the military plans to expand its digital defence force to 5,000 by 2030.

In May, a similar cyber defence exercise will take place in Tallinn, Estonia, bringing together NATO allies for a joint test.