1. An apparatus for reconfiguring a technical system based on analysis of the security of said technical system, said apparatus comprising: an input for receiving technical information characterizing the technical system; a graph representation unit configured to provide, based on the received technical information, a representation of potential attacks to the technical system in a directed graph of attack nodes having attributes related to the technical system; a ranking unit configured to provide a ranking list that ranks a number of different sets of countermeasures to enable a selected set of countermeasures to be taken to improve system security, each set of countermeasures comprising at least one countermeasure, wherein said ranking unit is configured to perform the following procedure for each set of countermeasures: logically applying the set of countermeasures to attacks in said directed graph; and determining a rank of the applied set of countermeasures based on the effectiveness of the applied set of countermeasures with respect to reduction of the risk of attacks; a selector configured to select among the sets of countermeasures having the highest rank; and a system reconfiguration unit configured to apply a selected set of countermeasures to the technical system.