http://hardware.slashdot.org/story/10/10/29/1456242/hiding-b...
http://www.cisco.com/web/about/security/intelligence/05_11_n...
If you really require references, then you have not been paying attention.
The NSA back-door in Cisco hardware has been known since at least 1997, when I first found out about it.
There are lots and lots of links to be found if you look. They aren't even hidden.
Just know, that NOTHING you do online is out of view of the NSA.