The NATO Cooperative Cyber Defence Centre of Excellence (CCDCOE) in Tallinn, Estonia, is hosting this week the Locked Shields 2025 cyber defense exercise.
Described as one of the world’s most complex cybersecurity exercises, Locked Shields 2025 has gathered nearly 4,000 experts representing 41 NATO ally and partner nations. The number of participants is roughly the same as in the previous year.
The goal of Locked Shields is to test and improve the preparedness of national cybersecurity teams in defending national systems and critical infrastructure, including telecommunications networks and military infrastructure, through a realistic simulation.
At Locked Shields 2025, 17 blue teams have been tasked with defending 8,000 virtual systems (hosted on a cyber range operated by CR14 Foundation) against thousands of sophisticated attacks.
This year’s cyber defense exercise also brings challenges related to quantum computing and AI.
Participants must not only fend off cyberattacks, but also deal with disinformation, political pressure, and infrastructure issues. They have been tasked with navigating legal aspects and strategic communications in high-pressure scenarios.
“The world is witnessing a clear rise in cyberattacks against critical infrastructure,” said Mart Noorma, director of the NATO CCDCOE. “We see it daily in Ukraine, where energy grids and communications systems are targeted, but also globally, from ransomware attacks on hospitals to disruptions in public services.”
“Locked Shields prepares nations to defend not only their networks but the essential services their societies depend on. As cyber threats grow more complex and the lines between peace and conflict blur, Locked Shields stands as a reminder that resilience is not built in isolation — it is forged through shared challenges, trusted cooperation, and relentless training,” Noorma added.
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