Polish team won third place in NATO Cyber Defence Exercise Locked Shields 2015. The Polish team included members from CERT Polska team. The winners this year was NATO CIRC team, and Estonian team took second place. The theme of the exercise is defending a simulated network of a fictious country from a wide spectrum of attacks. The defended network consists of two ISP-s, a power plant, a set of voice services, office networks with Windows and Linux workstations and a drone command center. The objective of the defenders is twofold: to protect the network from the attacks, but also to provide appropriate service level for the end-users of the network. The secondary objective was to coordinate efforts with teams of other defended countries. The attacks were varied – from DDoS and BGP hijacking to preinstalled backdoors and MITM-ing of unsecured connections. Novelty this year were utilization of the IPv6 protocol and adding a reconneissance drone control center to the network. The exercise is organized and managed by NATO Cooperative Cyber Defence Centre of Excellence. This year, 14 teams took part.