Apple boasts that users have downloaded more than 3 billion iPhone apps since it opened the App Store. But no one is certain how many pirated iPhone apps are downloaded as well.

One estimate, at financial news Web site 24-7 Wall Street, puts losses due to piracy at $450 million, split between Apple and the developers who would otherwise profit from a paid download. Rogue app stores such as Cydia cater to iPhone users who have unlocked - or jailbroken - their devices to bypass Apple's restrictions. Jailbroken iPhones can operate on networks other than AT&T's, feature customized graphics, and access applications from providers other than the App Store.