The largest and most advanced international live-fire cyber defense exercise in the world, Locked Shields 2016, began April 18 and was to continue through April 22, according to the organizer, the NATO Cooperative Cyber Defense Center of Excellence (CCDCOE).

This annual event operates as a scenario-based real-time network defense exercise to focus on training experts who protect national information technology (IT) systems daily.

Locked Shields 2016, organized by the CCDCOE since 2010, includes over 550 participants and 26 countries. It has 20 Blue Teams that represent 19 nations and the NATO Computer Incident Response Capability (NCIRC), which are tasked to maintain the networks and services of a fictional country, Beylia, under strong pressure.

The defenders tasks are to include handling and reporting incidents, solving forensic challenges, as well as responding to legal, media, and scenario injects, the event website said.

The event organizers gather at the CCDCOE’s home of Tallinn, Estonia, but participating Blue Teams access the exercise online and typically work from their home countries, NATO said.

Locked Shields 2016 is focusing on realistic technologies, networks, and attack methods, NATO said. This is to stay abreast with market developments. During the exercise over 1,700 possible attacks will be carried out against the Blue Teams with over 15,000 virtualized systems deployed. The virtualized Blue Team networks are custom-built and consist of a variety of platforms and services, the CCDCOE said in a statement.

The CCDCOE noted one issue the Blue Teams will have to do is maintain a number of servers, online services, and an industrial control system (ICS).

NATO also highlighted this year the exercise is seeing a record number of joint teams.

Locked Shields 2016 was organized in cooperation with the Estonian Defense Forces, Finnish Defense Forces, the Swedish Defense College, the British Army, United States European Command, and other partners.

The CCDCOE is a NATO-accredited knowledge hub based that focuses on interdisciplinary applied research and development concerning cyber security. It includes consultations, training, and information-sharing among NATO members, allies, and partners in cyber defense.