DHCP as in it's an ethernet connection to a residential router that provides the device with connectivity details.
Normally this isn't considered as secure as a bad actor can cut the power or connecting cables (e.g. If you're using dsl) to kick your system offline.
And, yeah, my old security system absolutely had an old 2G/EDGE modem to connect and send basic signals (as a fallback, in case of the above power cutting scenario). Was great.
A rather infamous Reddit employee/administrator who's generally regarded as being responsible for the Golden aga of IAMA on Reddit (as she personally vetted and brought in some big name AMAs).
She was let go, which was one of the first instances of Reddit's foray into the realm of anti-community bullshit.