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IDG News Service - Apple Inc. has just over a day left to patch a bug in its iPhone software that could let hackers take over the iPhone just by sending out an SMS (Short Message Service) message.

The bug was discovered by noted iPhone hacker Charlie Miller, who first talked about the issue at the SyScan conference in Singapore. At the time, he said that he had discovered a way to crash the iPhone via SMS, and that he thought the crash could ultimately lead to working attack code.

Since, then he has been working hard, and he said he's able to take over the iPhone with a series of malicious SMS messages. In an interview Tuesday, Miller said he will show how this can be done during a presentation at the Black Hat security conference in Las Vegas on Thursday with security researcher Collin Mulliner.

"SMS is an incredible attack vector for mobile phones," said Miller, an analyst with Independent Security Evaluators. "All I need is your phone number. I don't need you to click a link or anything."

Miller reported the flaw to Apple about six weeks ago, but the iPhone's maker has yet to release a patch for it. Apple representatives could not be reached for comment, but the company typically keeps quiet about software flaws until it releases a patch.

If it does release a pre-Black-Hat patch, Apple will not be alone. Microsoft Corp. had to scramble to put out an emergency fix for a flaw in its Active Template Library (ATL), which is used to build ActiveX controls. That "out-of-cycle" patch was released Tuesday, ahead of another Black Hat presentation on that particular vulnerability.

Miller's attack doesn't pop up shellcode -- the basic software attackers use as a steppingstone to launch their own programs on a hacked machine -- but it lets him control the instructions that are within the phone's processor. With some more work, someone could take this exploit and run shellcode, Miller said.

Although it's an old technology, SMS is emerging as a promising area of analysis as security researchers use the powerful computing capabilities of the iPhone and Google Inc.'s Android software to take a closer look at the way SMS works on mobile networks.

On Thursday, two other researchers, Zane Lackey and Luis Miras, will show how they can spoof SMS messages that would normally only be sent by a carrier's servers. This type of attack could be used to change someone's phone settings simply by sending him an SMS message.

Miller believes that more SMS bugs are likely to emerge. To help find them, he and Mulliner have developed an SMS "fuzzing" tool that can be used to hammer a mobile device with thousands of SMS messages without actually sending the messages over the wireless network (a costly endeavor).

The tool, which he calls the Injector, runs on the iPhone, Android-based devices and Windows Mobile phones.

The tool inserts itself between the phone's computer processor and the modem and makes it look like the SMS messages are coming through the modem when in fact they're being generated by the phone.