Hybrid conflict is said to exist when certain, often non-military instruments of power are orchestrated and strategically deployed as weapons, without this amounting to armed conflict. Examples of such instruments include political subversion, cyber activities, disinformation, economic destabilisation, corrupt financial practices and actual attacks on critical infrastructure. These are activities which undermine our open society and our democracy under the rule of law, and which take place below the threshold of force, in other words without crossing the legal boundary between war (in the sense of armed conflict) and peace. The threats tend to occur in domains in which the armed forces do not traditionally operate, in the grey zone between war and peace. Hybrid threats, both national and international, are mainly designed to undermine society as a whole, thus putting societal resilience under pressure.In its advisory report, the AIV discusses the multifaceted phenomenon of hybrid threats from three different perspectives: physical, virtual and cognitive. The physical dimension relates to the world as we experience it through sensory perception. The virtual dimension concerns the processing, protection and dissemination of information. The cognitive dimension is the entirety of perceptions, observations and intentions in society. In addition to the obvious threats in the physical dimension, the AIV focuses in particular on the impact of hybrid activities (or attacks) on the virtual and cognitive dimensions, given that governments find it very difficult to anticipate this type of threat effectively in terms of policy. Physical attacks tend to be more visible and easier to attribute. Furthermore, it is usually clear from the outset who is responsible for physical security and protection; generally speaking, this is also fairly well organised. By contrast, there is much uncertainty about virtual and cognitive attribution and protection.