The SmartScreen connection uses SSLv3 just fine on my machine. Here's an example payload: https://gist.github.com/3448961 https://gist.github.com/3448961 (I ini

The SmartScreen connection uses SSLv3 just fine on my machine. Here's an example payload: https://gist.github.com/3448961 https://gist.github.com/3448961 (I initially posted this on HN directly, which broke the site layout, so I deleted that post -- sorry about that!) The base-64 encoded strings in the request are the HTTP referrer and the download location, respectively. The "client key" and "MAC" seems to be API key-like authenticators. Not sure what the GUIDs are about. Anyway, the use of this data has been explained in quite a bit of detail a long time ago already: http://windows.microsoft.com/en-US/windows-vista/smartscreen-filter-frequently-asked-questions http://windows.microsoft.com/en-US/windows-vista/smartscreen.... As said elsewhere already, the feature is easy enough to turn off. And there is definitely an opt-in question somewhere, as I had to enable the feature on my machine in order to test it...