I was pissed to learn that arris DOCSIS modems do not allow you, the owner, to install firmware updates or adjust most settings. Only the ISP gets to do that.
Earlier versions of cable modems had flaws that allowed consumers to push configs on the ethernet port and uncap their cable modems and gain higher speeds than they had paid for.
"Thank you for upgrading your service to our VVVIP Price Tier! Your first three months as a VVVIP customer is 50% off..."
They did, but the overhead at the time was high. And they generally didn't peruse unless you were causing trouble....or slipped up on OPSEC.
Cable ISP network security back in the day was horrid. SNMP string would get leaked. With that you could snmpwalk the entire node you were on. It was amusing.