World's largest cyber defense exercise Locked Shields brings together over 3000 participants

Tallinn, Estonia – From 18 to 21 April, the NATO Cooperative Cyber Defense Center of Excellence (CCDCOE) is hosting Locked Shields 2023, the world’s largest live-fire cyber defense exercise. Over 3,000 participants from 38 nations are taking part in the exercise, which involves protecting real computer systems from real-time attacks and simulating tactical and strategic decisions in critical situations.

Locked Shields is a Red Team vs Blue Team training exercise, with Blue Teams composed of NATO CCDCOE member nations and their partner nations. In addition to defending systems, teams must report incidents, execute strategic decisions, and solve forensic, legal, and media challenges. The exercise plan was prepared by 400 organizers, creating more than 5,500 virtual systems for its purpose.

“No other cyber defense exercise can offer as specialized and detailed of an experience as Locked Shields can. 24 Blue Teams from around the world must keep critical infrastructure and IT systems up and running. Teams can demonstrate how well they can keep systems running under real-life situations and high pressure,” said NATO CCDCOE director Mart Noorma.

In addition to the technical aspects, strategy and cooperation play an equally important role in Locked Shields. “Technical specialists cannot solve a cyber crisis alone. Usually, decision-makers and experts from different governmental bodies and walks of life are those who try to repel the attacks,” explains Noorma. “This is why, in addition to cyber defense, we focus on strategy games, legal issues, and crisis communication at Locked Shields. Cooperation must we swift, because a large cyber attack can quickly escalate into a large-scale security crisis, and these kinds of exercises allow us to be better prepared,” added Noorma.

The Blue teams represent national cyber Rapid Reaction Teams, deployed to assist a fictional country under large-scale cyber attacks. Their task is to protect the mock state’s information systems and critical infrastructure from thousands of attacks, make management decisions in a crisis situation, and ensure that decisions are well considered.

In Locked Shields 2022, the Finnish Blue Team came out on top by demonstrating solid network and web defenses, and they excelled in situation reporting.

Locked Shields has been organized in Tallinn by the NATO Cooperative Cyber Defense Center of Excellence (CCDCOE) since 2010.

The media day for the exercise will take place on April 18. To participate, please write to [email protected]. Learn more about last year’s Locked Shields exercise here.


The CCDCOE is a NATO-accredited knowledge hub offering a unique interdisciplinary approach to the most relevant issues in cyber defense. The heart of the CCDCOE is a diverse group of international experts from the military, government, academia, and industry, currently representing 39 sponsoring and contributing nations. The CCDCOE encourages and supports the process of mainstreaming cybersecurity into NATO and national governance and capability within its closely connected focus areas of technology, strategy, operations, and law. The CCDCOE is also responsible for identifying and coordinating education and training solutions in the field of cyber defense operations for all NATO bodies across the Alliance.