iOS 5 Prevents Wire-Tapping on GSM iPhone with Unsecured Call Feature

June 11, 2011 — by Farrukh Zafar2



iOS 5 Prevents Wire-Tapping on GSM iPhone with Unsecured Call Feature

June 11, 2011 — by Farrukh Zafar2

You might have already been moved by the so many new features that the new iOS 5 brings, and as we discover it more and more, we come to know more about it. As we earlier told in the top 10 features of iOS 5 beta comes with so many cool new features such as the Notifications Center, iMessage, iCloud, Banner alerts and even the option of deleting individual calls from iPhone which we discussed here, apart from so many other features that are yet to be discovered.

But the feature that still hadn’t heard of in iOS 5 is the Unsecured Call alert. This new feature of iOS 5 actually issues a popup alert when you receive an incoming call from an unrecognized number or from a blocked caller ID. Here’s what appears on the iPhone screen as a consequence:

Unsecured Call : The cellular network you are using is not encrypted, This call can be intercepted by unauthorized listeners.

The science behind this new feature is the fact that hacks and security breaches can actually make listening in on to your phone calls possible, brining in use, IMSI catcher, a fake GSM cell tower.

Here’s a proper definition of an IMSI catcher described by Defcon:

“A fake GSM base station designed to trick the target handset into sending you its voice traffic.”

It’s a genuine problem with all GSM phones and they actually point the user by displaying a small emblem if encryption is not used. This could be an exclamation mark. The calling number is also a pointing factor, as the receiver fails to see the number of the caller, while the network access is managed by the SIM of the IMSI-catcher.

So how iOS 5 protects you from one kind of wiretapping is by issuing the “Unsecured Call” alert when your iPhone rings. The wiretapping hack described above is easily possible, otherwise, on any GSM iPhone on AT&T carrier.

Although the message alert doesn’t seem to threat you, it at least gives you an idea to think twice before taking the call, because the incoming source seems apparently sinister.

Another reason to love iOS 5? We’ll keep you posted as more things are discovered. We’ve heard the new-feature tally exceeds 200!

Farrukh Zafar

Farrukh Zafar is the inside-out gadget guy at Simonblog. You can always reach him at Twitter.com/fariZafar

  • The title of this is misleading: this feature (available in all cell phones but rarely switched on) alerts the caller to the fact that the call is unencrypted call rather than “prevent wiretapping”.

    The latter suggests that the caller can make a secure call if this message does not appear – this is not true. The call can still be intercepted by a passive attack (that decrypts the call), or attacks at different places on the network eg in the carrier’s fixed line network, via call recording malware on the device, attacks on the bases station or air interface interception on the recipients device.

    Although the feature ‘prevents wiretapping’ by warning the user not to make the call in the first place, this is similar to not using a cell phone at all.

    For a full description of the vulnerabilities and various attacks, Cellcrypt has created an educational whitepaper that can be found here: http://www.cellcrypt.com/sites/default/files/users/Cellcrypt%20Voice%20Security%20Brief%20WPVSB0110LEV3.1.pdf

  • toysandme

    Will iOS 5 finally allow call recording? Apple has made it impossible so far but I see that the UK will make it compulsory by the end of this year :