Wireless sensor networks (WSN) consist of a large number of tiny sensor devices that have limited power and limited sensing, computation, and wireless communications capabilities. Sensor nodes usually operate in unattended and even harsh environments, and as a result, sensor nodes are prone to failures and are vulnerable to malicious attacks. Therefore, for reliable and secure computation and communication in WSN, fault tolerance and intrusion tolerance become two essential attributes that should be designed into WSN. In this paper, we study state-of-the-art fault tolerance and intrusion tolerance techniques for WSN and propose a new fault-intrusion tolerant routing mechanism called MVMP (multi-version multi-path) for WSN that will support highly reliable and secure sensor networks. Follow-up work on the MVMP to be carried out in the near future is also discussed.