Back when I was attending community college, I had my own personal laptop and wanted to get on the Internet to work on my assignments. In those days, they provided banks of computers for us instead of WiFi. In order to get online, I used the following process for months:

Log on to one of those computers.
Find the MAC address.
Change my laptop’s wired Ethernet interface’s MAC address.
Unplug the Ethernet cable from the computer and plug it into my laptop.
Ran the DHCP client.

I eventually got caught because one of the IT guys saw what I was doing. They said that they’d been noticing some strangeness the entire time I’d been doing it and told me te stop.