iPhone supports some basic security mechanisms, including SSL; mail authentication methods and VPN's, as well as WPA and WPA2 for WiFi access.

iPhone has a passcode lock feature. When enabled, you must enter a four-digit code every time you wake iPhone from standby. It also prevents transferring photos to your PC or Mac; you must disable the passcode lock to transfer photos.

We don't know how robust the passcode lock is, though, and it is generally not good practice to store very sensitive information on mobile phones, PDA's or laptops without encryption. We recommend not storing anything sensitive on your iPhone for now, passcode or not.

Another open question is whether iPhone can be reset by iTunes to bypass the passcode lock, yet remain activated for service by AT&T. If so, this would enable anyone to crack an iPhone and use it as a phone and Internet device, though perhaps without retrieving your personal information.

iPhone supports L2TP and PPTP VPN's (virtual private networks), but we didn't have a VPN set up for testing, so we don't know how well this works.