In its efforts to defeat a request from the Electronic Frontier Foundation to give jailbreaking the iPhone an exemption from DMCA protection, Apple is merely looking to protect the cell towers of its partner carriers like AT&T. In a response filing to answer questions from the U.S. Copyright Office, Apple said that malicious hackers could use jailbroken iPhones to make anonymous and/or free calls, to bump other users off the network, or to even render cell towers inoperable.

"By hacking the BBP software through a jailbroken phone and taking control of the BBP software," Apple wrote in its filing, "a hacker can initiate commands to the cell tower software that may skirt the carrier's rules limiting the packet size or the amount of data that can be transmitted, or avoid charges for sending data. More pernicious forms of activity may also be enabled."

"For example," the company warned, "a local or international hacker could potentially initiate commands (such as a denial of service attack) that could crash the tower software, rendering the tower entirely inoperable to process calls or transmit data."

The EFF had requested an exemption for the iPhone to protect it against charges of violating the Digital Millennium Copyright Act, which, among other things, prohibits decrypting security protections in computers and other devices, and imposes stiff penalties for numerous copyright violations.

There have been no test cases against hackers (either among the tinkerer or malicious variety) for jailbreaking the iPhone, though Apple has issued take-down notices to at least one site for posting information relating to jailbreaking and hacking the iPhone.

In addition, Apple hasn't done very much in the way of directly trying to stop jailbreaking (though one iPhone OS update did brick jailbroken phones). An exemption from the DMCA, however, would make it more difficult for the company to take action in the future, should it want to do so, and would make take-down notices that much harder to enforce.

In its response filing with the U.S. Copyright Office, Apple makes the argument that protecting the iPhone from jailbreaking or hacking is in the customer's best interest, of paramount importance to its carrier partners, and better for the public at large.

An exemption, according to the company, presents threats to the following:

• Crashes & instability
• Malfunctioning & safety
• Invasion of privacy
• Exposing children to age-inappropriate content
• Viruses & malware
• Inability to update software
• Cellular network impact
• Piracy of developers’ applications
• Instability of developers’ applications
• Increased support burden
• Developer relationships
• The Apple/iPhone brand
• Limitation on ability to innovate

You can find more information in the full filing.