First of all, I find the notion that the UK would send a SUBMARINE to log on to the INTERNET rather silly...
I'm sure their department of defense has internet access... no need to go wifi war-diving :)
That said - and assuming you intended to present the more plausible scenario of hacking into the protected wifi network of the coastal palace of . Connecting surveillance equipment directly to the ships network would be extremely poor practice, not matter what operating system it is running.
Such systems are usually isolated.
As for internal threats - soldiers bringing media onboard from home and such: from my experience in the field, such military systems are usually hardened in a manner that you would need a set of wrenches, the admin password, and some wires and assorted spare hardware in order to plug in something you brought from home. This has yet to stop soldiers from doing so - but in this case the correct approach is disciplinary - since I doubt any security system, on windows or any other os, could stand between a sailor on a six month underwater mission and his porn.
Hopefully they have non networked recreational PCs for that purpose...
