DefHack 2026: Students Face a Simulated Cyberattack

Master’s students in Cybersecurity at ISTIC (University of Rennes) took part in DefHack, a cyber crisis management exercise designed to challenge them with the technical and human aspects of a cyberattack.

A French Navy frigate at the heart of the scenario

How should you respond when a computer system is compromised? This was the scenario presented to students on ISTIC’s CISO specialisation and Science of Software and Hardware Security specialisation.

Over several hours, they had to investigate a simulated attack targeting a French Navy frigate. Detecting the intrusion, analysing threats, auditing systems and defining remedial measures: the teams had to identify vulnerabilities and determine how to restore the affected services.

This scenario formed part of the 2026 edition of DefHack, held from 5 to 16 October at several higher education institutions across France. In total, nearly 600 students from 17 institutions took part in this initiative led by the French Cyber Defence Command (COMCYBER), with the participation of the Direction générale de la sécurité extérieure (DGSE) and Direction générale de l’armement – Maîtrise de l’information (DGA MI).

Coordinating teams under pressure

When faced with an attack, technical expertise alone is not enough. Participants must also allocate roles, prioritise urgent tasks and share relevant information to ensure a coordinated response. Events unfold rapidly, priorities shift and decisions must be made within a limited timeframe.

This immersive exercise gave students the opportunity to step into the shoes of cyber combatants and gain practical insight into the challenges of defensive cyber operations. They were able to appreciate the importance of coordination, communication and stress management — all essential factors in responding effectively to an incident.

The day concludes with an after-action review to analyse the decisions made, the difficulties encountered and potential areas for improvement. The aim is not necessarily to resolve every problem, but to understand the dynamics of a complex crisis and learn how to tackle it collectively.

Exploring careers in cyber defence

Beyond putting their skills into practice, DefHack 2026 gives students the opportunity to discover the range of roles involved in the armed forces’ cyber defence operations and the variety of missions they encompass. The exercise also provides an opportunity to explore entry routes and career prospects within the French Ministry of the Armed Forces, both in military and civilian roles.

For ISTIC students, this immersive experience complements their academic training, helping them understand the operational realities of defensive cyber operations and explore career opportunities in the sector.