The popularity of any technology helps to determine its susceptibility to hackers, viruses and other intrusions. A platform that is widely used simply makes it worthwhile to take the time to construct the means of intrusion. The iPhone is no exception, although in this case the story begins with illegally altering the smartphone's structure to free it from the Apple storefront.
Many cell phones and smartphones are is some ways tied into proprietary systems, and there are many users who take steps to "unlock" them or, in the case of iPhones, "jailbreak" them. These are somewhat different concepts, but nevertheless similar in their alteration of the basic configuration of the units. The problem that the procedures open up for the users is that the units are them exposed to risks that they were never designed for. In the case of the iPhone, this risk has shown itself in the spread of a new worm, called "Duh", that focuses on stealing online banking data. The cost could be tremendous, both for the immediate user and for other systems that the particular smartphone might be tied into. Read more in this article.