Multipath routing minimizes the consequences of security attacks deriving from collaborating malicious nodes in MANET, by maximizing the number of nodes that an adversary must compromise in order to take control of the communication. In this paper, we identify several attacks that render multipath routing protocols more vulnerable than it is expected, to collaborating malicious nodes. We propose a novel on-demand multipath routing protocol, the Secure Multipath Routing protocol (SecMR) and we analyze its security properties. The SecMR protocol can be easily integrated in a wide range of on-demand routing protocols, such as DSR and AODV.