The Russian Federation has been waging a hybrid war campaign against NATO and the EU for years. The Kremlin has so far skillfully managed to exploit the vulnerabilities of the West. The NATO Eastern flank members are particularly exposed to the Kremlin-orchestrated systematic subversion and this is a problem of growing significance to the Alliance as it is undermining its cohesion and is preventing the build-up of strong national security and defense systems of its Eastern European member states. In order to effectively remedy this dangerous situation, the Eastern flank NATO member states must immediately start implementing a coherent national institutional capacity building programs, supported by NATO and the EU, aimed at timely mitigation of existing vulnerabilities and building up long-lasting resilient national security structures able to tackle hybrid threats coming from any direction. To carry out this ambition, a number of capacity building steps are proposed.