Downloading a "free USB jailbreak" for the Xbox 360 is generally a futile and risky endeavor. True modification of the console requires hardware expertise and soldering (JTAG or RGH). Users are advised to be skeptical of any website promising a software-only solution, as these are almost exclusively scams or malware traps.
First, we need to clarify terminology. Unlike the PlayStation 3 (which had a softmod via USB for a specific firmware version), the Xbox 360 never had a true "one-click USB jailbreak." Xbox 360 Jailbreak Usb Software Download Free