MANET routing protocols are designed based on the assumption that all nodes cooperate without maliciously disrupting the operation of the routing protocol. A large number of attack types of varying severity are threatening MANET. Dynamic Source Routing (DSR) is a well-known reactive MANET routing protocol that does not support security of routing messages. In this paper, we study the performance of both DSR and its flow-state extension routing protocols in the presence of blackhole, grayhole, selfish and flooding attacks. We conclude that the performance of flow-state DSR is better than DSR in the presence of all attacks. Flooding attacks are found to dramatically impact all the standard performance metrics. Blackhole attacks significantly worse the packet delivery ratio in a static network using unmodified DSR. All the attacks greatly increase the end-to-end delay; an effect particularly marked in a static network.