— Traditional network routing uses the single (shortest) path paradigm. This paradigm leaves the session vulnerable to a variety of security threats, such as eavesdropping. We propose to overcome this via dispersive routing, conducted over multiple paths. This increases significantly the costs inflicted on an attacker who wishes to eavesdrop sessions by hijacking network links (or routers). We formulate the Security Traffic Manager (STM) problem (route session fragments1 , over multiple paths, so that protection against an attacker, with a known hijacking budget, is guaranteed) and the attacker problem (find the cheapest hijacking strategy). The problems are analyzed for cases in which the attacker must eavesdrop all the fragments as well for cases in which it must eavesdrop only a fraction of them. We analyze the theoretical complexity of these problems and offer algorithms for finding dispersive routes that guarantee security. Though some theoretical cases of the problem are shown ...