We propose a new analytical method for determining whether nonsupersymmetric
probe branes embedded in nontrivial backgrounds are perturbatively stable or
not. The method is based on a relationship between zero mass solutions of the
relevant DBI equations of motion and tachyonic solutions. Furthermore, due to
the above relation, the question, of whether a classical solution is stable or
not, can be answered simply by studying the derivatives of that solution with
respect to its integration constants. Finally, we illustrate the efficiency of
this method by applying it to several interesting examples.Comment: 18 pages; introductory material added in Section 2, journal versio