How do we determine what is proportionate? If some valuable intellectual property, such as part of the designs for the US's latest fighter jet the F35, which were hacked in 2009. [1] Then what can be the response to this? Can it simply be the cost of developing this design? If so then what about the strategic loss the state has suffered, how can that be calculated in? So long as it is excluded state sanctioned cyber-attacks will not be deterred.  [1] Gorman, Siobhan, Cole, August, and Dreazen, Yochi, ‘Computer Spies Breach Fighter-Jen Project’, The Wall Street Journal, 21 April 2009,