Many plain routing protocols have been proposed for mobile ad hoc net- works. These protocols all assume cooperative networks and focus only on routing effectiveness and efficiency. However, mobile ad hoc networks are not a friendly environment for various reasons in nature. Routing Proto- cols without any security feature can put entire network at risk. As security becomes an increasingly important issue, secure mobile ad hoc routing is attracting more and more research attention. In this paper, we make a comprehensive investigation on the issue of network security and conduct an up-to-date survey of secure mobile ad hoc routing protocols.