http://news.hitb.org/content/scariest-ipv6-attack-scenarios
Experts are reporting a rise in the number of attacks that take advantage of known vulnerabilities of IPv6, a next-generation addressing scheme that is being adopted across the Internet. IPv6 replaces the Internet's main communications protocol, which is known as IPv4.
IPv6 traffic being tunneled across IPv4 networks, particularly using the Teredo mechanism that is built into both Microsoft Windows Vista and Windows 7. This vulnerability with IPv6-over-IPv4 tunneling has been known for at least five years, but it is still being exploited.