21/05/2026
At 2026, teams from NRENs across Europe and beyond faced a high-intensity cybersecurity challenge: a Capture the Flag (CTF) competition designed and hosted by RNP, the Brazilian NREN.
The competition tested everything from OSINT and web security to forensics, cryptography, and governance. Teams raced to uncover hidden "flags" across simulated systems and networks, balancing speed, strategy, and collaboration under real-time pressure.
The winners? Dimitris Kolotouros and Marios Levogiannis from ΕΔΥΤΕ - Εθνικό Δίκτυο Υποδομών Τεχνολογίας και Έρευνας - GRNET. Their approach was simple but effective: start with easier challenges to build momentum, then tackle the harder ones strategically. The turning point came with an AI sandbox escape challenge that required unconventional thinking and cross-disciplinary knowledge.
"A critical skill is understanding when to disengage from a challenge and return later. Spending too long on a single problem can reduce overall performance," said Marios.
Beyond the rankings, the real value was in the shared experience: teams learning when to persist, when to pivot, and how to think collectively under pressure.
👏 Congratulations to the GRNET team, and thank you to RNP for bringing this challenge to the community.
🔗 Read the full story: https://connect.geant.org/2026/05/12/security-days-2026-capture-the-flag-inside-a-high-intensity-cybersecurity-challenge
