  We study the parameterized complexity of the optimal defense and optimal
attack problems in voting. In both the problems, the input is a set of voter
groups (every voter group is a set of votes) and two integers $k_a$ and $k_d$
corresponding to respectively the number of voter groups the attacker can
attack and the number of voter groups the defender can defend. A voter group
gets removed from the election if it is attacked but not defended. In the
optimal defense problem, we want to know if it is possible for the defender to
commit to a strategy of defending at most $k_d$ voter groups such that, no
matter which $k_a$ voter groups the attacker attacks, the outcome of the
election does not change. In the optimal attack problem, we want to know if it
is possible for the attacker to commit to a strategy of attacking $k_a$ voter
groups such that, no matter which $k_d$ voter groups the defender defends, the
outcome of the election is always different from the original (without any
attack) one.
