Unlike the first generation iPhone, the iPhone 3G must be activated in the store in most countries.[183] This makes the iPhone 3G more difficult, but not impossible, to hack. The need for in-store activation, as well as the huge number of first-generation iPhone and iPod Touch users upgrading to iPhone OS 2.0, caused a worldwide overload of Apple's servers on July 11, 2008, the day on which both the iPhone 3G and iPhone OS 2.0 updates as well as MobileMe were released. After the update, devices were required to connect to Apple's servers to authenticate it, causing many devices to be temporarily unusable.[184]