National Security interests in the Internet Infrastructure

I'm trying to write a paper on possible National Security interests in
the internet infrastructure. I know that's a little vague, but anything
you have that might be interesting/remotely relevant to that topic would
be a great help.

Examples might be:
- Any technological weaknesses in the current system that a nation-state
or hostile organization might try to exploit.
- How hostile elements are currently making use of the internet to
communicate (terrorists?).

Anything you have would be a great help. Official-ish documents
(reports issues by government agencies, testimonies in front of
Congress, etc.) would be particularly helpful.

Thanks.

--
Neil.