In my opinion, the current state-of-art in computer security focuses on building walls: they are effective for establishing a perimeter but they do not adapt to the ever changing conditions (unless a human expert intervenes, of course). I am more interested in adaptive solutions, which are similar to guards in the sense that they are capable of observing, adapting and reacting to the environment. Within this general view, here is a short summary of what I have worked on so far. Descriptions below are by no means complete but intended to give the reader an idea of what I have been working on. For more information on my research, please feel free to contact me.