Traceroute is probably the most famous computer networks diagnostic tool, widely adopted for both performance troubleshooting and research. Unfortunately, traceroute is not free of inaccuracies. In this poster, we present our ongoing work to address the inaccuracy caused by third-party addresses. We discuss the impact of third-party addresses on traceroute applications and present a novel active probing technique able to identify such addresses in traceroute traces. Finally, we detail preliminary results suggesting how this phenomenon has been largely underestimated. Categories and Subject Descriptors C.2.1 [Computer-communication networks]: Network Architecture and Design—Network topology General Terms Measurement Keywords Traceroute, Internet topology, AS-level path.