## 1 Introduction
However, due to the limited network resources and energy-constrained nature of nodes, it is expected that some nodes will exhibit uncooperative behaviours. These behaviours may adversely affect the overall network performance and put a further strain on the limited energy of the cooperative nodes. Specialised protocols have been employed in the network layer of nodes in MANETs to ensure collaboration among nodes. It is usually expected that these nodes will carry out their operations in compliance with the protocol specifications. However, these expectations are not always met. Nodes sometimes make local decisions on whether to follow the network's basic operations or not. These nodes may decide to act selfishly by not participating in route discovery processes or deceitfully by responding to some route requests, but ensuring that the corresponding data packets are dropped. These misbehaving nodes specialise in conserving their limited energy resources, while the good nodes consume their own energy to ensure that the network is operational. An increase in the number of nodes exhibiting these types of behaviours may result in reduced network efficiency. Countermeasures for node misbehaviour and selfishness are mandatory requirements in MANETs. Selfishness that causes a lack of node activity cannot be solved using classical security means that aim at verifying the correctness and integrity of an operation. It is therefore essential to employ a management system that will ensure an effective and reliable collaboration of all nodes in a MANET. An effective reputation management system would ensure that a node attains a certain reputation level before it can effectively operate in a network. This would ensure a gradual reduction or elimination of misbehaving nodes trying to disrupt the operations of the network [13]. In this paper, we propose a novel approach in monitoring the packet transmission activities of mobile nodes. The reputation of nodes is evaluated using a data-driven weighted average approach, which is based on the number of successfully transmitted data and control packets that a node carries out for other nodes as against its own transmitted packets. The distinctive direct monitoring approach employed in the proposed dynamic reputation management system is effective at detecting and mitigating various misbehaviours exhibited by nodes in a MANET. The use of directly obtained information to evaluate the reputation of nodes ensures that nodes do not rely on second-hand information before evaluating the reputation of its neighbours. This eliminates the possibility of obtaining false second-hand information, which can be used to carry out attacks, such as bad-mouthing and ballot-stuffing, as described in [14; 15; 16; 17]. Furthermore, the reliance on directly obtained information will help in reducing routing overhead and in decreasing additional energy requirements. The rest of the paper is organised as follows: Section 2 contains related works on trust and reputation management systems in MANETs. Section 3 discusses issues concerning misbehaving nodes in MANETs. Section 4 presents the proposed dynamic reputation management system. Section 5 presents details of the implementation work. Section 6 presents the simulation results and analysis. Section 7 concludes by setting out the benefits of the proposed system and outlines future research works.