From: David Carlisle <davidc@xxxxxxxxx>

I think you'll find that IE has the hooks, it just needs someone to hook
to them,

http://msdn.microsoft.com/workshop/networking/pluggable/overview/overview.asp

...
A pluggable MIME filter is an asynchronous pluggable protocol that
receives data through a stream, performs some operation on the data, and
returns a data stream. The output data might be in a different format
from the original stream.