Cyber Shield 2018 is a simulation exercise featuring a cyber attack scenario, with the national-level decision makers, gathered in the Homeland Security System Board, had the opportunity to test the functioning of the crisis management situations..The Exercise was conducted in the Ministry of Defence on 15 March 2018, by the Co-ordination members and representatives of other institutions. “New security threats necessitate timely response, and the Exercise “Cyber Shield 18“ was an excellent opportunity for the strategic level to test the knowledge and the awareness of the existing procedures and legislation. Bearing in mind the recent events, the synergy of all components of the Homeland Security Systems, the Croatian Armed Forces and of the local communities is essential to assist the population cope with natural disasters“, said the Defence Minister Damir Krstičević. The Main Exercise Authority was the CIS Sector of the Croatian Ministry of Defence, headed by Colonel Bruno Bešker who was the Director of the Exercise, The Exercise was managed by the Main Planning Group, including the representatives of the Office to the President of the Republic, of the Office to the Prime Minister, Office of the National Security Council, the Security and Intelligence Agency and the Military Security and Intelligence Agency, the Information Systems Security Bureau, of the Ministry of the Interior, of the Faculty of Electronic Engineering and Computing, of the Ministry of Defence and of the Croatian Armed Forces. “Cyber Shield 2018 is a national-level exercise of response to cyber threats by the elements of the Homeland Security System. The objective is to raise the awareness of cyber threats and to highlight the role of the Homeland Security System Board, and underline the importance of strategic communication in crisis situations, and of the co-ordination and collaboration of the public, the academic and the business sectors. It also aims to raise the discussion on the strategic-level operating guidance and to point to the potential challenges involved in a cyber crisis“,explained Colonel Bešker, the Exercise Director.  “Cyber Shield“ was conducted as a table-top exercise. The participants analysed several potentially harmful activities according to a fictitious scenario, and made the adequate decisions to ninimise the potential damage of the activities in the scenario, and later discussed the dionika. The participants and observers commended the organisation and conduct of the exercise as “a first step towards full synergy of the Homeland Security System as a overall goal“. The dependence on the communications and information systems creates vulnerabilities that can be a target of enemy attacks – either individuals, hacker groups, criminal organisations and terrorists, whose technical properties and motivation can vary, but share the interest in government bodies and critical national infrastructure. In the situation characterised by growing cyber threats, particularly as Advanced Persistent Threats, conducted by well-trained experts, the synergy of all relevant national shareholders of cyber safety is the key to successful cyber defence and to achieving actual national safety. The EU predicts point to a considerable increase in cybercriminal activity within the next 5-year period and equallises it with the traditional criminality- The cybercriminality is in constant increase in the EU (up to 20% of total crimes) and in the Republic of Croatia as well. Cyber criminality is following the development of the digital society., and results from the many problems in the existing systems. Cyber battlefield is composed of connected communications-information systems. The attackers can investr a small effort to inflict serious damage to the infrastructure or to the economy of the attacked country, particularly if it is using the CIS systems to a significant extent in support to business processes (e.g. extensive computerisation of government offices). The attackers’ may have various goals: to manipulate with information, to spread panic, damage or destroy the key infrastructure (power plants, communication systems, railways, road signalisation, banks etc); the attacks can also serve to collect information.