A black hole attack is a severe attack that can be easily employed against routing in sensor networks. In a black hole attack, a malicious node spuriously announces a short route to the sink node (the destination) to attract additional traffic to the malicious node and then drops them. In this paper, we propose a hierarchical secure routing protocol for detecting and defending against black hole attacks. The proposed protocol uses only symmetric key cryptography to discover a safe route against black hole attacks. The comparison of the proposed protocol with two other existing approaches proves that the proposed scheme is faster in detecting black hole attacks with much lower message overhead.