I remember seeing modded cable modems or devices that allow you to spoof and hijack a nearby residences internet and cable packages back on IRC warez sites in late 2008-2010. I remember one guy got arrested for selling them and it made headlines for a little, but surely there is still a market for things like this or devices that perform a similar service?
I did some initial research and found some relevant news articles. http://www.wired.com/2009/11/derengel/
http://www.haxorware.com/forums/showthread.php?tid=1337 this says that the exploit has been patched so to speak with traditional plug and play methods. Have new methods been implemented?
Never mind the usage of the darknet, the FCC will shit in your cheerios and then waterboard you with them if you use a hacked modem. There's a ton of federal law and multiple carrier lines being crossed with your communications. Don't get caught with that shit.
Source: Telecommunications Tech for 5 years.