Executive Summary

NATO has completed its annual flagship cyber defense exercise, Cyber Coalition 2025, hosted in Tallinn, Estonia. The exercise brought together around 1,500 cyber defenders from 29 Allied nations and seven partner countries, including Ukraine and Japan. The primary objective was to bolster the alliance's ability to defend its networks and operate collectively in cyberspace. Participants were immersed in a realistic scenario involving hybrid attacks on the critical infrastructure of a fictional island nation, forcing them to coordinate defensive actions across military and national boundaries.

Exercise Overview

Cyber Coalition is NATO's premier annual collective cyber defense exercise and has been running since 2008. This year's event took place over one week and was managed from NATO's Cyber Security Centre in Estonia. The core of the exercise was a complex, fictional scenario where participants had to defend the nation of "Andravia" from attacks by the rival nation "Harbadus" on the island of "Occasus-Icebergen."

Key features of the exercise included:

• Large Scale: Approximately 1,500 participants from 36 total nations.
• Realistic Scenarios: The exercise featured seven concurrent storylines based on real-world cyberattacks observed over the past year.
• Hybrid Warfare Focus: The simulations emphasized the spillover effects of cyberattacks on land, sea, and air operations, reflecting the nature of modern hybrid conflicts.

Simulated Threats

The scenarios were designed to test a wide range of defensive capabilities. Participants had to respond to various incidents, including:

• An attack on a Critical National Infrastructure (CNI) system.
• A threat hunting mission to find an adversary hidden within a nation's data backups.
• The defense of a satellite communications provider against a sophisticated cyberattack.

Each participating team was given only a limited view of the overall conflict, requiring them to share intelligence and coordinate their responses effectively to build a complete operational picture and successfully defend the targeted systems.

Impact Assessment

Exercises like Cyber Coalition are crucial for maintaining and enhancing the defensive posture of the NATO alliance. They serve several key purposes:

• Enhancing Interoperability: They test and improve the ability of diverse national cyber defense teams to work together seamlessly, using shared procedures and communication channels.
• Testing Capabilities: The exercise allows NATO and its partners to test new defensive tactics, tools, and procedures against the latest adversary tradecraft.
• Strengthening Deterrence: By publicly demonstrating a robust and coordinated cyber defense capability, NATO signals its readiness to counter aggression in cyberspace, contributing to the alliance's overall deterrence posture.
• Building Trust: Collaborative problem-solving in a high-pressure environment builds trust and personal relationships between cyber defenders from different nations, which is invaluable during a real crisis.

Lessons Learned

While specific outcomes are classified, the overarching goal is to identify gaps in coordination, technical capabilities, and information sharing. The lessons learned from Cyber Coalition will be used to refine NATO's cyber defense doctrine, improve training programs, and guide future investments in cybersecurity technology and personnel. The exercise reinforces the understanding that cyber defense is a team sport, requiring constant practice and adaptation to stay ahead of evolving threats.

Mitigation and Preparedness

The exercise itself is a form of mitigation, falling under the category of D3FEND Decoy Environment at a strategic level. Key defensive principles practiced during the exercise that are applicable to all organizations include:

1. Incident Response Planning: Develop and regularly test incident response plans that involve multiple teams and stakeholders.
2. Information Sharing: Establish clear protocols for sharing threat intelligence with trusted partners, both internally and externally.
3. Defense in Depth: Implement layered security controls across networks, endpoints, and applications to ensure that a single failure does not lead to a catastrophic breach.
4. Resilience and Recovery: As demonstrated by the backup-hunting scenario, organizations must not only defend against attacks but also ensure they can recover critical systems and data after an incident.