It is a Red team vs. Blue Team exercise, where the latter are formed by member nations of CCDCOE. In 2021 there were 22 Blue Teams participating with an average 40 experts in each team. The Teams take on the role of national cyber Rapid Reaction Teams that are deployed to assist a fictional country in handling a large-scale cyber incident with all its implications. The Exercise in 2021 involved about 5000 virtualised systems that were subject to more than 4000 attacks. The teams must be effective in reporting incidents, executing strategic decisions and solving forensic, legal and media challenges. To keep up with technology developments, Locked Shields focuses on realistic scenarios and cutting-edge technologies, relevant networks and attack methods.