Locked Shields 2026: 41 Nations Strengthen Cyber Resilience in World’s Biggest Exercise

The world’s largest live-fire cyber defense exercise, Locked Shields 2026, concluded on Friday after bringing together more than 4,000 participants from 41 nations.  Organized by the NATO Cooperative Cyber Defence Centre of Excellence (CCDCOE) in Tallinn, Estonia, the event simulated intense real-time cyberattacks against critical infrastructure and military systems, testing defenders’ ability to maintain essential services under pressure. The number of participants was the same as in 2025. Teams were tasked with protecting air defense, e-voting platforms, and other critical infrastructure. In addition to technical skills, Locked Shields tests the ability to deal with disinformation and political pressure. According to Tõnis Saar, Director of the NATO CCDCOE, participants demonstrated strong capabilities in detecting and responding to malicious activity. Saar emphasized the need to translate exercise lessons into real-world readiness, particularly as AI continues to reshape both cyber defense and attack capabilities. Sixteen multinational teams competed in the exercise. The three highest-scoring joint teams, listed in no particular order, were France and Sweden; Latvia and Singapore; and Germany, Austria, Luxembourg, and Switzerland.  Exercise Director Dan Ungureanu underscored the event’s core objective: enhancing international collaboration, building trust, and developing a shared understanding of cyberspace resilience.  Locked Shields has evolved significantly over the past 16 years. When the first exercise was held in 2010, only four nations and 60 individuals participated. Related: Over 370 Organizations Take Part in GridEx VIII Grid Security Exercise Related: Apple iPhone and iPad Cleared for Classified NATO Use Related: AI Can Autonomously Hack Cloud Systems With Minimal Oversight WRITTEN BY Eduard Kovacs Eduard Kovacs (@EduardKovacs) is senior managing editor at SecurityWeek. He worked as a high school IT teacher before starting a career in journalism in 2011. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering. 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