My guess is that no, it's not about pub/sub specifically, but rather that "you" can address & subscribe arbitrary hosts anywhere on the internet via a naive imp

My guess is that no, it's not about pub/sub specifically, but rather that "you" can address & subscribe arbitrary hosts anywhere on the internet via a naive implementation. Segregating your 'dumb' controller/sensor nodes and restricting their ability to talk elsewhere via routing, firewalling or proxies would reduce the risk of a single crappy device leaking onto the internet. At the cost of some centralisation of control in your gateway/router/whatever, of course. And you still need some form of crypto on your local network to protect against local/physical attackers. Is it a coincidence that this post comes a few days after CF announces a "private network for IoT"[1]? My wirelessly-enabled Crystal Ball says no. I wonder if it's because the IoT is itself a big enough pie with current attention on (lack of) security, or if it's more to protect their main business from Mirai N+1/DDoSoT or whatever. [1] https://blog.cloudflare.com/orbit/ https://blog.cloudflare.com/orbit/