The popularity of the Xbox, as well as (in the United States) its comparatively short 90-day warranty, inspired efforts to circumvent the built-in hardware and software security mechanisms, a practice informally known as modding. Within a few months of its release the initial layer of security on the Xbox BIOS (which relied heavily on obfuscation) was broken by MIT student Andrew Huang and the contents of the "hidden" boot ROM embedded on the MCPx chip was extracted using some custom built hardware. Once this information was available, the code was soon modified so that it would skip digital signature checks and media flags, allowing unsigned code, Xbox game backups, etc., to be run. This was possible due to flaws in the Xbox's security.[38] Modding an Xbox in any manner will void its warranty, as it may require disassembly of the console. Having a modified Xbox may also disallow it from accessing Xbox Live, if detected by Microsoft, as it contravenes the Xbox Live Terms of Use,[39] but most modchips can be disabled, allowing the Xbox to boot in a "stock" configuration. Softmods can be disabled by "coldbooting" a game (having the game in the DVD drive before turning the console on, so the softmod is not loaded) or by using a multiboot configuration.

There are four main methods of modding the Xbox:

Modchip: installing a modchip inside the Xbox that bypasses the original BIOS, with a hacked BIOS to circumvent the security mechanisms.[40] TSOP flashing: reflashing the onboard BIOS chip with a hacked BIOS to circumvent the security mechanisms. The Xbox BIOS is contained on a commodity EEPROM (the 'TSOP'), which can be made writable by the Xbox by bridging points on the motherboard.[41] Flashing is usually carried out by using a specially crafted gamesave (see 'Game save exploit', below) to flash the onboard TSOP, but the TSOP can also be de-soldered and re-written in a standard EEPROM programmer. This method only works on 1.0 to 1.5 Xboxes, as later versions replace the commodity TSOP with an LPC ROM contained within a proprietary chip.[42] Softmods: installing additional software files to the Xbox hard drive, which exploit