The Dutch government believes that public-private cooperation is an essential corner stone to achieve its policy goals of keeping the internet a secure, trusted and free space. The principle of public-private cooperation guides various policy initiatives, such as the (second) National Cyber Security Strategy, currently under development by the Ministry of Security and Justice in close cooperation with the Ministry of Economic Affairs, other departments, the private sector, academia and civil society. Also the Ministry of Economic Affairs is currently developing its vision towards the Internet for the mid-term period. This workshop is organized by the Ministry of Economic Affairs in close cooperation with the Dutch National Cyber Security Centre and touches on the necessity of exploring new forms of cooperation in sharing relevant data for cyber security. From an international comparative study into national and international cooperation concerning online threats the organizers learned that pro-active and, for a substantial number of state actors even, reactive cooperation and data-sharing is hard to impossible to achieve due to very different, but negative reasons . IGF 2012 Workshop #87 on ‘Cross border cooperation in incidents involving (Internet) Critical Infrastructure‘ concluded with several recommendations. An important one was that the different expert groups, public and private, on cyber security and enforcement seem to function too much in isolation, as if in a silo. The panel concluded that these silos need to be broken down in order to be able to share relevant data, learn to understand each other and actually cooperate in order to achieve enhanced cyber security and more efficient enforcement of perpetrations in the cyber realm. At the same time it was pointed out that cooperation between industry itself was not necessarily a common thing and sharing data between public and private entities got stuck in discussions on data protection questions. “Breaking down silos” sounds easy, but these experts notice that it is mostly not happening and if it is, not (fast) enough. “We discuss it and then we go home”. The organizers has noted this and is keen on hearing best practices from around the world in order to be able to judge whether this could be an example for Dutch national policy that presently is being drafted. At the same time The Netherlands is able to show its own best practices to other countries, including “the Dutch model” of the NCSC. This open forum will bring best practices together from around the world and debate e.g. the following questions: How should “breaking down silos” be interpreted?; Who are actually addressed?; Who need to break down silos? Is it necessary to make someone responsible for this task?; What are the opportunities and challenges?; What is the aim of this approach and is this clearly defined? What steps need to be undertaken, if a global solution is needed? In the open forum we bring together current initiatives with industry and governments, to discuss best practices, lessons learned and potential steps forward that will enhance cyber security and cyber enforcement significantly in the coming years. In the future new forms of cooperation will build bridges to enhance cyber security, create the potential for joint actions and enlarge the potential for public-private partnerships that ensure a better cyber security and pushes back (organized) crime from the internet. Finally, the bottom line often is that issues like security, privacy and openness/freedom of speech cannot be solved at a national or even regional level, as the internet is a true global medium. However, so far, attempts to solve these issues internationally/globally, have failed because of the differences in cultures, values, norms and legislation. Discussions are being held continuously, without really making any progress; there seems to be an invisible glass ceiling stopping us... What are suggestions for a way forward?