Exploiting iPhone Safari Tap-to-Dial Feature

Via SPI Dynamics Blog -

The Apple iPhone’s Safari web browser has a special feature that allows the user to dial any phone number displayed on a web page simply by tapping the number. SPI Labs has discovered that this feature can be exploited by attackers to perform various attacks, including:

• Redirecting phone calls placed by the user to different phone numbers of the attacker’s choosing
  
• Tracking phone calls placed by the user
• Manipulating the phone to place a call without the user accepting the confirmation dialog
• Placing the phone into an infinite loop of attempting calls, through which the only escape is to turn off the phone
• Preventing the phone from dialing
  

These types of attacks can be launched from a malicious website, from a legitimate website that has Cross-Site Scripting vulnerabilities, or as part of a payload of a web application worm.

For example, an attacker could determine that a specific website visitor “Bob” has called an embarrassing number such as an escort service. An attacker can also trick or force Bob into dialing any other telephone number without his consent such a 900-number owned by the attacker or an international number. Finally, an attacker can lock Bob’s phone forcing Bob to either make the call or hard-reset his phone resulting in possible data loss.

SPI Labs researchers reported these issues to Apple on July 6 and are working with Apple to remediate the problems. However, SPI Labs recognizes the unique urgency of these issues and the large number of people that could be affected. As such, SPI Labs recommends that iPhone users do not use the built-in Safari browser to dial telephone numbers until Apple resolves these issues.

------------------------

Billy presented this research at SPI Con 2007 last week in Atlanta, GA.