From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

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. However, uncapping may be considered an illegal activity, such as theft of service.[1]


There are several methods used to uncap a cable modem, by hardware, software, tricks, alterations, and modifications.

One of the most popular modifications is used on Motorola modems (such as the SB3100, SB4100, and SB4200 models); by spoofing the Internet service provider's TFTP server, the modem is made to accept a different configuration file than the one provided by the TFTP server. This configuration file tells the modem the download and upload caps it should enforce. An example of spoofing would be to edit the configuration file, which requires a DOCSIS editor, or replacing the configuration file with one obtained from a faster modem (e.g. through a Gnutella network).

An alternate method employs dhcpforce. By flooding a modem with faked DHCP packets (which contain configuration filename, TFTP, IP, etc.), one can convince the modem to accept any desired configuration file, even one from one's own server (provided the server is routed, of course).

Another more advanced method is to attach a TTL to the modem's RS-232 adapter, and get access to the modem's console directly to make it download new firmware, which can then be configured via a simple web interface. Examples include SIGMA, a firmware add-on that expands the current features of an underlying firmware, and others.

See also[edit]


  1. ^ McMillan, Robert (November 2, 2009). "Cable modem hacker busted by feds". Computerworld. IDG News Service. Hackers have known for years that certain models of cable modem, [sic] such as the Motorola Surfboard 5100, can be hacked to run faster on a network, a process known as uncapping. However, the question of whether uncapping a modem is illegal is "not clear."

External links[edit]