In this paper, we consider the problem of choosing disks (that we can think
of as corresponding to wireless sensors) so that given a set of input points in
the plane, there exists no path between any pair of these points that is not
intercepted by some disk. We try to achieve this separation using a minimum
number of a given set of unit disks. We show that a logarithmic approximation
to this problem can be found in polynomial time using a greedy algorithm. To
the best of our knowledge we are the first to study this optimization problem.