'I recently got a cheap home security system ..."
(Reasonably) secure fix I use:
Setup one system as a ZoneMinder server. Add chrony, bind.
Add another subnet to that system.
Move all the cameras to that new subnet. Turn off updates, change any 'phone home' service addresses, etc.
Be sure the ports used by the cameras can't be addressed from WAN side. (Your router DOES have firewall. etc, right?)
More to it, of course. And lots of variations.
To the original OP of this thread:
Unless your wallet is encased in a ferro-shield of some sort - you should be more worried about walking down the street than caring that someone wants to steal info from inside your home network. Who are you? Does anyone care? If you had a real need for some serious security you would have it or it would far too late already, I guarantee.
We all accept the possibility of stealth attacks with the cars we drive, the phones we use, and just walking into a public building with security cams.
You just have to believe that MOST people are good and want to Do The Right Thing.
If you knew how much someone else really knows about you - any/all of you - you would not be able to sleep at night. You just have to trust.
You are playing with the PI - chip from Broadcom. With as many of those chips as has been produced, if you look at the spec sheet for it - do you think that is the OFFICIAL spec sheet? Research that for a crazy, fun ride. I did that long before I came here. I would invite a reply from one of the PI people, but I have never, ever seen even a comment from them about the spec sheets. Really scary NDA, I expect. No surprise. And I don't think they are Agents of The Enemy.
But - none of this will stop me.
I trust - a little. You just have to work within the system where you are. There isn't any 'out west' to flee to, any more - physical or virtual. So here we are.
(Not like I wanted to put a damper on this fun discussion, though.)
Now, if you really want a nighttime scary story, research who owns and operates the content server companies that echo just about everything you see on the web. Most of the first of them were ex-FED security people. What do they say about coincidence?
Oh, coincidence that we hear more about the content-resellers doing what comes natural in a 'free' economy?
Sorry. That title '... Spy Novel ...' seems to have hit a nerve. I apologize.