If you get a strange text message containing only square box any time after today, you might be the victim of an SMS hack that could leave your iPhone totally exposed to a would-be hacker. How do you avoid it? Short of a patch from Apple, your only recourse is to power down your iPhone as quickly as possible.

Charlie Miller, a noted security researcher, discovered the hack a month ago and contacted Apple, but the company has yet to release a software update fixing the security hole. Miller and fellow researcher Collin Mulliner will make the exploit public at Thursday's Black Hat cybersecurity conference.

The hack involves sending a series of SMS messages to hijack the iPhone. At that point, the hacker could control all functions of the iPhone, and could even use it to hijack more iPhones.

This isn't the only news of security risks associated with the iPhone. Forensics expert Jonathan Zdziarski recently bypassed the iPhone 3GS's passcode PIN and backup encryption with relative ease.