1. Method for adapting security policies of an information system infrastructure in function of attacks comprising the steps of: storing potential attacks and their associated risks in a data repository; storing curative security policies in response of the potential attacks in a data repository; monitoring entering contents representing data streams of the information system; detecting at least one attack in the information system; assessing a success probability parameter of the at least one detected attack and its associated cost impact parameter; assessing an activation impact parameter of at least one curative security policy in response to the at least one detected attack and its associated cost impact parameter; deciding of the activation or deactivation of a curative security policy in function of the success probability parameter of the, at least one, detected attack, of the activation impact parameter of at least one curative security policy and of the cost impact parameters of both the detected at least one attack and the at least one curative security policy.