In vehicular delay-tolerant networks (VDTNs),
an end-to-end relay path between bundle source and destination
nodes may not be available. To accomplish such
goal, VDTNs rely on nodes cooperation. Thus, in order to
maintain network efficiency, it is very important to ensure
that all network nodes follow the protocol. This is not an
easy task since nodes may diverge from the protocol due
to a selfish behavior or to maintain their data or resources
integrity. This paper proposes a cooperative watchdog system
to detect and act against misbehavior nodes in order
to reduce their impact in the overall network performance.
Its operation relies on a cooperative exchange of nodes
reputation along the network. By detecting selfish or misbehaving
nodes, it is possible to improve the overall network
performance. Conducting simulation experiments considering
the VDTNSim tool and the Spray-and-Wait routing
protocol shows that the cooperative watchdog proposed
for VDTNs is not only effective in detecting misbehaving
nodes but also contributes to improve the overall network
performance by increasing the bundle delivery probability
and decreasing the amount of resources waste.