NATO's Locked Shields 2026 Cyber Exercise Tests 4,000 Defenders Against 8,000 Live-Fire Attacks

Executive Summary

NATO's Cooperative Cyber Defence Centre of Excellence (CCDCOE) has successfully concluded its annual flagship cyber defense exercise, Locked Shields 2026. Hosted in Tallinn, Estonia, the exercise brought together over 4,000 cyber defenders from 41 allied and partner nations in the world's most complex live-fire cyber defense drill. Participating teams, organized into 16 multinational Rapid Reaction Teams, worked remotely to protect the critical infrastructure of 'Berylia,' a fictional nation under intense, coordinated cyberattack. Over several days, these teams faced approximately 8,000 live attacks targeting a mix of conventional and specialized IT systems. A notable addition this year was the inclusion of an electronic voting system, challenging defenders to secure democratic processes against sophisticated threats. The exercise aims to enhance multinational cooperation and readiness in a realistic crisis scenario.

Exercise Overview

Event: Locked Shields 2026 Organizer: NATO Cooperative Cyber Defence Centre of Excellence (CCDCOE) Participants: Over 4,000 individuals from 41 NATO and partner nations. Objective: To practice and improve the defense of national IT systems and critical infrastructure in a realistic, high-pressure environment. The exercise is not just a technical challenge but a holistic test of a nation's ability to respond to a large-scale cyber crisis.

Scenario Details

The exercise simulates a wartime scenario where national cyber Rapid Reaction Teams are deployed to assist a fictional country. The teams must maintain the services and networks of this country while under constant attack from a dedicated 'Red Team' of aggressors. The 2026 iteration included a diverse range of targets:

• Critical Infrastructure: Power grids, 5G mobile networks, satellite management systems.
• Military Systems: Bespoke military IT networks and communication platforms.
• Government Systems: For the first time, a full-scale electronic voting system was included, requiring teams to defend it against manipulation and disruption.

Beyond fending off the 8,000 technical attacks, teams were scored on their performance in several other areas:

• Strategic Decision-Making: Reporting incidents to leadership and making strategic choices under pressure.
• Legal Analysis: Operating within the bounds of international law.
• Digital Forensics: Investigating attacks to determine attribution and methods.
• Strategic Communications: Managing public information and media during a crisis.

Impact Assessment

Locked Shields is a proactive measure designed to improve global cybersecurity resilience, particularly among NATO allies and partners. The direct impact is the enhanced skill and readiness of the thousands of participating cyber defenders. By simulating attacks on complex, real-world systems, the exercise exposes gaps in technology, processes, and international cooperation that can be addressed before a real crisis occurs. The inclusion of an e-voting system reflects the evolving threat landscape and the recognition that protecting democratic processes is a critical national security function. The lessons learned from Locked Shields directly inform the development of national cyber defense strategies, joint operational playbooks, and the technical capabilities of participating nations, ultimately strengthening the collective defense of the alliance.

Detection & Response Lessons

The exercise provides a controlled environment to test and refine detection and response capabilities.

• Integrated Defense: Success requires integrating technical data from SIEMs and EDRs with strategic intelligence and legal guidance. Teams that excel are those that can quickly move from detecting an anomaly to understanding its strategic impact.
• Cross-Domain Cooperation: The exercise forces cooperation between IT security teams, OT (Operational Technology) engineers, legal advisors, and public affairs officers. This simulates the multi-faceted nature of a real-world cyber crisis.
• Threat Hunting: With 8,000 attacks, teams cannot simply wait for alerts. Proactive threat hunting based on hypotheses about the adversary is essential for finding stealthy intrusions.

Mitigation Recommendations

The core purpose of Locked Shields is to identify and practice mitigation strategies.

• Resilience through Design: The exercise highlights the need to build resilient systems that can withstand and continue to operate during an attack, rather than just focusing on prevention.
• Public-Private Partnership: The complexity of the simulated environment, built with industry partners, underscores the necessity of strong public-private partnerships in defending critical infrastructure.
• Continuous Training: The key takeaway is that cyber defense is a perishable skill. Regular, realistic exercises like Locked Shields are crucial for maintaining a high state of readiness. Organizations should conduct their own internal tabletop and live-fire exercises to test their response plans.