No, LLMs can definitely be useful for cyber too. It's the whole reason the US government banned Claude Fable for export.

An LLM can not just try existing exploits like a script kiddy, but with iteration it can try variations and if you know what runs on the server, inspect the source for potential exploits.

They can also look at your setup and say what issues they see (reverse proxy config, etc).

Doesn't replace an expert, but can be useful for a first pass before you get the highly paid people involved.