There is no intrinsic physical reason that the difficulty of 'defending' a system is symmetric with the difficulty of 'attacking' it.

For instance, it is not because you are able to design and release a (biological) virus that you are also able to defend from it (design a vaccine and inoculate the world's population).

If we're lucky, it might be the case for many instances of problems, but there is no a priori guarantee that this holds.