Эта запись в блоге написана более 14 лет назад, поэтому может быть неактуальной.
Anonymization vulnerability in Windows fixed
It has been discovered that the IPv6 tunneling behaviour in Windows Vista and 7 can cause problems for anonymization. Users of Windows Vista or 7 should upgrade to version 23 which disables the IPv6 tunneling. It can also be disabled by hand.