It's pretty well taken for granted today that IPv6 is the future of TCP/IP communications, even though most networks haven't yet made the transition. The exhaustion of IPv4 networks, however, makes it only a matter of time. IPv6 has many advantages over its predecessor and it includes security mechanisms, but it's not invulnerable. In fact, some of its benefits can be exploited; for instance, IPv6 is more dependent on auto configuration via router advertisements. Unfortunately, fake router advertisements and NAT-PT can be used to intercept traffic that would normally use IPv4.
Find out more, including how to protect against this man-in-the-middle attack, here: