1. A non-transitory computer readable storage medium storing program code for controlling a computer to estimate a safety level of a circuit by determining a residual error probability for the circuit, the program code comprising: a component modeller, which is adapted to receive a vector of error probabilities, each error probability associated with one of a number of bit lines of the circuit, and the component modeller being furthermore adapted to model a change of the vector of error probabilities due to a behaviour of a system component, in order to output a changed vector of error probabilities as vector of residual error probabilities, wherein the component modeller is adapted to receive a vector of attack error probabilities and to output a change of the vector of error probabilities due to a behavior of a system component based on the vector of attack error probabilities as vector of residual error probabilities, wherein the vector of attack error probabilities includes an attack error probability for each of the number of bit lines of the circuit, wherein an influence of a disturbed bit line to the attack error probability associated with a bit line proximate to the disturbed bit line is reflected in the attack error probability vector or the change of the vector of error probabilities.