They were. But times have changed and lots of organisations that have or refer to "Unix" in their name are now no longer focused only on that operating system.
OK. (Proves that I haven't been doing my homework. ;-)
I'd suggest you visit one of the conferences of the mentioned organisations. Then you'll see that they cover a broad range of issues outside those related to Unix alone.
I would, if there was time and money ...
Computing by itself doesn't bring much risk. Computing with broken or "contaminated" software brings risks. Even more so does networking, since it's the ideal "carrier" for all risks related to computers in general. So the organisation really should be closely related to networking, or in close contact with an an organisation related to networking.
Definitely, but we mustn't forget the thousands of stand-alone PC:s that only have foot-net. Diskettes are just as bad. We must also bear in mind the large non-connected multi-user systems, where local cracking can be just as painful as network cracking (although it's less common these days - agreed). Best regards, /Liman