Methods and architectures for automatic filter generation are described. In an embodiment, these filters are generated in order to block inputs which would otherwise disrupt the normal functioning of a program. An initial set of filter conditions is generated by analyzing the path of a program from a point at which a bad input is received to the point at which the malfunctioning of the program is detected and creating conditions on an input which ensure that this path is followed. Having generated the initial set of filter conditions, the set is made less specific by determining which instructions do not influence whether the point of detection of the attack is reached and removing the filter conditions which correspond to these instructions.