I have no proof one way or the other if Anthropic or OpenAI have "properly secured corporate networks". Both seem like fast changing places with lots of servers and workers. Seems most likely to me that someone somewhere made a mistake or missed something due to all the change and their network is not 100% secure.
But even if their networks are secure, I think that spies who are willing to coerce people, trick people and go in person to data centers or offices could find a way to get those models and other things.
Aren't the models also distributed to various data centers--i think it's very easy with resources
It depends how secure they are. But yes - in reality they are only a couple of TB, so just distributing the models and their source code (not their training data) it feasible.
I mean, the source for claude code was "leaked" by accident so at least some of their processes are not that secure. I feel that they are more like a Startup then a Enterprise (ignoring finances).