Cable modems that have been hacked, or "uncapped," allow users to anonymously tap into Internet access offered by broadband providers and set their own upload and download rates, officials say. It's a gray legal area that federal prosecutors in New York have waded into for the first time by charging a Pennsylvania man who allegedly sold such devices, ABC News reported Tuesday.

Prosecutors say Thomas Swingler trafficked in unlawful access devices for his online business Cablehack.net, whose Web site sells "pre-modded" Motorola Surfboard modems for between $38 and $58 that can be customized by the owner without a cable company's knowledge, the U.S. broadcaster said.

The devices can have legitimate uses, which puts them in a legal gray area. ABC said Swingler states on his Web site, "If you decide to use one of these modems to get free Internet, then you're committing theft of service and we will take no responsibility for what may happen to you if you're caught."

Swingler declined to comment to ABC News.