And they thought I was crazy as a teenager in the 90's to study Amateur Radio and Microwave communications. A friend of mine does embedded development, so we worked together and reverse engineered a Motorola modem and built our own. It ignores nearly every packet the ISP sends down for control and just reports itself as the Motorola modem that we pulled apart. Its highly secure since it doesn't do much than convert QAM-encoded packets and turn them into Ethernet frames; firmware updates and configuration require plugging a JTAG header into the thing.
Anon because of how many FCC rules and regulations I am violating doing this, despite the analog coming off of this thing is cleaner than, and behaves much better overall, than the piece of crap I am masquerading as.