Devices participating in mobile ad hoc networks (MANET) are expected to strictly adhere to a uniform routing protocol to route data packets among themselves. Unfortunately, MANET devices, composed of untrustworthy software and hardware components, expose a large attack surface. This can be exploited by attackers to gain control over one or more devices, and wreak havoc on the MANET subnet. The approach presented in this paper to secure MANETs restricts the attack surface to a single module in MANET devices a trusted MANET module (TMM). TMMs are deliberately constrained to demand only modest memory and computational resources in the interest of further reducing the attack surface. The specific contribution of this paper is a precise characterization of simple TMM functionality suitable for any distance vector based routing protocol, to realize the broad assurance that “any node that fails to abide by the routing protocol will not be able to participate in the MANET”.