This week, the world’s most complex cyber defence exercise, Locked Shields 2025, launches with full force in Tallinn, Estonia. Organised by the NATO Cooperative Cyber Defence Centre of Excellence (CCDCOE), the exercise challenges 41 different nations in 17 teams to defend national systems and critical infrastructure in a high-pressure, live-fire cyber conflict that mirrors today’s evolving threats.
“In a world where cyber threats cross every border, Locked Shields proves that resilience in cyberspace is built together,” said Mart Noorma, Director of the NATO Cooperative Cyber Defence Centre of Excellence. “Bringing nations, experts, and partners together in real-time defence is more vital than ever — and we are proud to stand at the heart of that mission.”
Celebrating its 15th anniversary, Locked Shields puts nations to the ultimate test. Participants must defend against relentless cyberattacks while dealing with political pressure, disinformation campaigns, and infrastructure crises. Success demands more than technical skills — teams must also manage legal complexities, strategic communications, and critical decision-making under intense time pressure.
The exercise addresses the protection of vital services and critical infrastructure that are fundamental for modern societies to operate, such as power and 5G networks, as well as key military infrastructure like air defence and battle management systems.
“In a cyber crisis, decisions must be made in seconds, under pressure, and without certainty,” emphasised Dan Ungureanu, Exercise Director of Locked Shields 2025. “Locked Shields teaches the mindset and cooperation needed to prevail when every second counts and every action matters.”
This year’s fictional scenario reflects pressing global realities, including geopolitical tensions, violations of sovereignty, and large-scale cyberattacks. The 2025 storyline has expanded to include additional fictional nations and wider regions, underlining how cyber defence cooperation must transcend borders in an increasingly interconnected digital world.
In addition, Locked Shields 2025 brings several major innovations to the battlefield. A new cloud segment has been created, quantum computing topics are now featured in the Strategic Decision-Making track, while AI challenges run across all main tracks. Multiple cyber operations and surprise elements have been planned throughout the two days of execution to test the teams’ speed and adaptability. Also, the strategic communication track is supported by a new dynamic information environment, and a unified storyline now links three major cyber exercises: Crossed Swords (XS), Locked Shields (LS), and Allied Power Exercise (APEX).
“The world is witnessing a clear rise in cyberattacks against critical infrastructure,” said Noorma. “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.
Nearly 4,000 cyber experts from 41 nations, both from NATO Allies and Partners, have come together for this year’s edition, building 17 multinational Blue Teams ready to face more than 8,000 sophisticated attacks against a massive landscape of 8,000 virtual systems representing nation state-like infrastructure. Hosted on the cyber range operated by CR14 Foundation and built by more than 400 organisers and experts worldwide, Locked Shields continues to be the premier environment where cyber defence, law, communications, and policy collide under intense pressure.