Locked Shields 2026: 41 Nations Train in Largest Cyber Defense

Executive Summary

The 2026 edition of Locked Shields, the world's largest and most complex live-fire cyber defense exercise, brought together 41 nations to test coordinated responses to simulated attacks on critical infrastructure, according to organizers. The exercise, run annually by the NATO Cooperative Cyber Defence Centre of Excellence (CCDCOE), has expanded dramatically from its inaugural edition in 2010, which involved only four countries. This year's scenario focused on defending a fictional island nation's power grid, telecommunications networks, and government systems against a sophisticated state-sponsored adversary.

Technical Analysis

Locked Shields 2026 required participating Blue Teams to defend a realistic, simulated national infrastructure comprising over 4,000 virtualized systems, including industrial control systems (ICS) for electrical distribution, SCADA for water treatment, and military command-and-control networks. The Red Team, composed of CCDCOE experts and volunteer ethical hackers, employed advanced persistent threat (APT) tactics including supply-chain compromise, living-off-the-land binaries, and custom malware targeting programmable logic controllers (PLCs).

Notable technical challenges included defending against a simulated ransomware variant that encrypted SCADA historian databases, a phishing campaign using deepfake audio of a fictional defense minister, and a coordinated distributed denial-of-service (DDoS) attack that peaked at 1.2 Tbps against critical DNS infrastructure. Teams had to implement network segmentation, deploy endpoint detection and response (EDR) tools, and conduct forensic analysis under time pressure while maintaining continuity of essential services.

Mitigations & Recommendations

Organizations should use the exercise's findings to strengthen their own incident response plans, particularly for cross-sector dependencies between energy, telecom, and government networks. Key takeaways include the need for pre-established communication channels with national CERTs, regular tabletop exercises that involve both technical and executive leadership, and investment in ICS-specific monitoring tools that can detect anomalies in operational technology (OT) environments. The CCDCOE publishes unclassified after-action reports and technical playbooks from each Locked Shields iteration, which are available to member nations and partner organizations.