Previous research in interdomain routing security has often focused on prefix hijacking. However,several prefix interception events have happened lately, which poses a new security challenge to the interdomain routing system. Compared to prefix hijacking, prefix interception is much harder to detect, as it avoids black hole by forwarding the hijacked traffic back to the victim. In this paper, we present a novel method to detect prefix interception. Our approach exploits a key observation about prefix interception: during a prefix interception event, the attacker detours the intercepted traffic through its network, which turns it into a new important“transit point” for access to the victim. By collecting data plane information to detect the emerging “transit point” and using control plane information to verify it, our scheme can identify prefix interception in real time.The results of Internet experiments and Internet-scale simulations show that our method is accurate with low false alarm rate(0.28%) and false negative rate(2.26%). Previous research in interdomain routing security has often focused on prefix hijacking. However, several prefix interception events have happened lately, which poses a new security challenge to the interdomain routing system. Compared to prefix hijacking, prefix interception is much harder to detect, as it avoid black hole by forwarding the hijacked traffic back to the victim. In this paper, we present a novel observation to prefix interception; the attacker detours the intercepted traffic through its network, which turns it into a new important “transit point ” for access to the victim. “By collecting data plane information to detect the emerging ” transit point "and using control plane information to verify it, our scheme can identify prefix interception in real time. The results of Internet experiments and Internet-scale simulations show that our method is accurate with low false alarm rate (0.28%) and false negative rate (2.26%).