1. A computerized method, comprising: controlling a computer to define at least one key event to be monitored by at least one agent; controlling the computer to create a graphical model for the at least one key event; controlling the computer to observe the at least one key event; controlling the computer to infer a degree of attack on the computer system based on an automated observation of the at least one key event in conjunction with a result of an effect the at least one key event has on the graphical mode, where controlling the computer to infer the degree of attack on the computer system comprises modifying a probability of attack on the computer system based on the observation of the at least one key event in conjunction with the result of the effect the at least one key event has on the graphical model; controlling the computer to monitor the output of the graphical model, the output indicating whether the probability of attack is greater than a threshold value; and controlling the computer to automatically adjust a security policy based on an output of the graphical model, where adjusting the security policy is performed automatically without user intervention, and where adjusting the security policy includes re-posturing a probabilistic security policy to correspond to the degree of attack; where the graphical model includes a plurality of nodes, where controlling the computer to create the graphical model for the at least one key event comprises controlling the computer to create at least one initial probability for nodes in the plurality of nodes in the graphical model and controlling the computer to adjust the at least one initial probability of at least one node in the plurality of nodes as a function of at least one statistical datum associated with a previous security attack, where the at least one initial probability is defined according to the probability security policy.