With DoD networks steadily adopting and transitioning to the next generation Internet Protocol, IPv6, careful consideration must be given to IPv6-specific implications on network protection. While Network Intrusion Detection Systems (NIDS) assist in protecting current IPv4 DoD networks, NIDS performance in operational DoD IPv6 environments is largely unknown. As a step toward more rigorous NIDS evaluation, we investigate the extent to which known IPv4 attacks are able to evade detection when converted to equivalent IPv6 attacks. Utilizing 13 general attack classes, we test the IPv6 readiness of two popular open source NIDSs: SNORT and BRO. Attacks in each class are evaluated in a virtual test bed that models both “native” and “transitional” networks. In the native IPv6 environment, we achieve a 95% detection rate for SNORT as compared to 8% with BRO. In addition, we discover a bug in SNORT where a carefully crafted IPv6 packet causes the NIDS to fail open, allowing full circumvention. Our findings suggest that, with respect to IPv6, both NIDS signatures and NIDS software require additional testing and evaluation to be operationally ready.http://archive.org/details/theunexploredimp109456800Lieutenant, United States Navy