ACLs, nothing, we've known about in-band signalling since forever and still this whole segment of the industry seems to either not know about it, or forgets about it at a cadence so regular it may as well not know about it.

System-level ACLs; mandatory or discretionary access control; secure-by-default application and network configurations are all for naught if you take an LLM, run it with all the privileges you'd have an accountable, judgemental operator, and then tell it to act based on arbitrary untrusted input which might include prompt injection attacks, something which cannot generally be sanitized.

Well-defined, well-enforced security policies can mitigate disasters, but many in the wild right now just don't account for this kind of threat model.