also, yet another reason I don't trust (and don't use) any ISP provided equipment. Remote administration from my ISP? No thank you.
You, I and most of the HN crowd may be well capable of maintaining a reasonably secure state of our own hardware and troubleshoot our way through common errors. However, the average internet user isn’t that experienced nor are most people interested in learning those skills.
but point well taken in general.
The firmware on whatever is doing docsis is going to be updatable by the ISP generally.
Two different mechanisms. The tr069 management and snmp triggered firmware upgrade
However, I would assume no unencrypted traffic is safe anyway, and the modem would indeed not have access to your internal network.