I hardly think apple or any company are dumb enough to name their backdoor publicly nsagate as a subdomain to their company's domain, it's probably some kind of service, since apple prefixes lots of things with NS (NextStep), it could also be initials for a billion other words, see
http://www.acronymfinder.com/NSA.html
well I guess it doesn't stand for next step a, or they didn't need any more names than 'a' and never went for 'b' ;)
Also it could be "Next Step Administration", "Next Step Access", etc.. there are a billion possibilities, I'm not saying apple doesn't give access to NSA, they surely do, but I'm saying they obviously won't do it this way ;)
> nmap -Pn -A -T4 nsagate.apple.com
Starting Nmap 6.40 ( http://nmap.org ) at 2014-03-23 21:27 CLST
Nmap scan report for nsagate.apple.com (17.254.0.48)
Host is up.
All 1000 scanned ports on nsagate.apple.com (17.254.0.48) are filtered
"In computer networking, port knocking is a method of externally opening ports on a firewall by generating a connection attempt on a set of prespecified closed ports. Once a correct sequence of connection attempts is received, the firewall rules are dynamically modified to allow the host which sent the connection attempts to connect over specific port(s). A variant called Single Packet Authorization exists, where only a single "knock" is needed, consisting of an encrypted packet.[1][2]
The primary purpose of port knocking is to prevent an attacker from scanning a system for potentially exploitable services by doing a port scan, because unless the attacker sends the correct knock sequence, the protected ports will appear closed."
