Just in case you missed a warning on Microsoft's Knowledge Base last week, be aware that its Internet Connection Firewall and its Basic Firewall do not block Internet Protocol Version 6 traffic.
And that this applies to:
But don't worry. Microsoft is recommending that you buy other firewall software that can filter and block IP version 6 traffic.
It rather charitably describes this as a "workaround".
News source: theinquirer.net