There are now tons of Certification Authorities (CAs) that are trusted by default in major OS's, many of which are unrecognizable without online lookup or reference. 

While there have been attempts by the NSA and others to "hack" or otherwise exploit root certicate authorities; is there anything preventing the NSA from becoming a Root CA itself? 

It certainly has the resources and expertise, and could "suggest" to major OS vendors to add its Root CA to the default trust store list (which is large enough that it may not be noticed by anyone..?) 

If it is feasible, what would the implications be? Could they essentially Man-in-the-Middle attack most HTTPS connections without a warning? (Perhaps not Dragnet-type interception, but close?) Or create a fake commercial root CA as obviously people would be suspicious if it had NSA plastered all over it?

It is already done:



It is the FPKI root CA, under explicit and full control of the US government. Windows already trusts it by default.

Before you flip out and begin to delete root CA certificates, burn your computer's motherboard, or drink a gallon of vodka, think about what it means. It means that the US government could technically emit a fake certificate for any SSL site that you are browsing -- but with a certificate chain that would point back to the US government. That is the point of having a "trusted CA" in the client: so that the client may validate a certificate chain. Therefore, such a forged site would hardly be a discreet way to eavesdrop on communications. All it would take would be a single user clicking on the padlock icon, reviewing the certificate chain, notice the FPKI root, and mock Obama on Twitter.

Pushing your own root CA in the "trusted store" of your victims is not an adequate way to spy on people without them noticing. Although it is a government agency, the NSA as a whole is usually not that stupid.
