Uncapping, in the context of cable modems, refers to a number of activities performed to alter an Internet service provider's modem settings. It is sometimes done for the sake of bandwidth (i.e. by buying a 512kbit/s access modem and then altering it to 10Mbit/s), pluggable interfaces (as by using more than one public ID), or any configurable options a DOCSIS modem can offer.
Uncapping may be considered an illegal activity, such as theft of service, and many Internet service providers check modem configuration files nightly to detect uncapped modems. If caught, uncappers risk possible account termination and/or prosecution for theft of service. Note that regardless of legality, uncapping may be a violation of the Terms of Service agreement that the customer has with the ISP.
Read more about Uncapping: Methods