In Wireless Mesh Networks (WMNs), mesh nodes cooperate and forward packets from each other in order to extend their communication range and reach nodes outside their transmission coverage. However, malicious nodes may refuse to cooperate by intentionally dropping packets in order to disrupt the integrity of network services. In this paper, we introduce a distributed and cooperative approach for detection of packet dropping attacks. Intrusion detectors are individually placed at each node to passively monitor the node behavior and exchange routing events and detection results with neighboring nodes. Based on the exchanged events, each node is able to instantly detect malicious behavior on the own node's communication link or in the neighborhood. A virtualized mesh network environment composed of virtual machines is used to implement the distributed detection approach and demonstrate its effectiveness and reliability for detecting packet dropping attacks in the mesh network.