Electrostatic Field-based Routing (EFR) is a form of geographical multi-path routing where packets are routed along a collection of electrostatic field lines, defined by electrostatic charges associated with source and sink nodes. EFR provides an efficient and scalable solution to the workload balancing problem. However, it assumes that nodes behave in a cooperative manner making EFR-based routing protocols vulnerable to various attacks. We investigate the security aspects of EFR-based routing protocols. We focus on an instance of EFR, called Multi-Pole Field Persistent Routing (MP-FPR), for which we identify attacks that can target different components of the protocol, and propose a set of corresponding defense mechanisms. We present extensive experimental evaluations of the impact of the different attacks and the effectiveness of the proposed defense mechanisms.