guess who’s texting you? evaluating the security of smartphone messaging applications (ndss...

Guess Who’s Texting You?Evaluating the Security of Smartphone Messaging Applications (NDSS Symposium 2012)Sebastian Schrittwieser, Peter Frühwirt, Peter Kieseberg, Manuel Leithner, Martin Mulazzani, Markus Huber, and Edgar WeipplSBA Research gGmbHVienna, Austria

Outline

• Introduction• Related Work• Mobile Messaging Applications• Evaluation• Results• Conclusion

Introduction

• In recent months a new generation of mobile messaging and VoIP applications for smartphones was introduced.

• These services with a novel user authentication concept offer free calls and text messages.

• The main contribution of our paper is an evaluation of the security of mobile messaging.

Introduction

Related Work

• User authentication is a popular field of research in information security, especially applied to distributed systems or for web services.

• Smartphone application security without mobile messaging services has been evaluated in the past.

• Recently, cloud storage services have attracted the interest of security researchers analyzing the implications of faulty authentication in that area.

Mobile Messaging Application

• All applications analyzed in this paper have one thing in common: They use the user’s phone number as the basis for identification.

• iOS don’t allow applications to access the phone number, but Android can.

• Benefit of typing number is that a WiFi-only tablet can be activated using the phone number of another device.

• Attacker could enter other’s phone number and hijack account.

Messaging Application

Evaluation

• Authentication Mechanism and Account Hijacking• Sender ID Spoofing/Message Manipulation• Unrequested SMS/phone calls• Enumeration• Modifying Status Messages

Authentication Mechanism and Account Hijacking

Attacker VictimServer

Victim’s phone Code(SMS)

Code

Code

Sender ID Spoofing/Message Manipulation

Attacker VictimServer

Message

Modify Sender ID

Unrequested SMS/phone calls

Attacker

Victim1

Server

Victim1’s phone Code(SMS)

Victim2’s phone

Victim2

Code(SMS)

Enumeration

Attacker Server

Attacker’s Address Book

Other user’s information

Modifying Status Messages

• We analyzed the protocol for setting the status message and explore possible vulnerabilities that could result in unauthorized modification of status messages.

• In practice, this approach would likely be combined with some sort of enumeration attack.

Experimental Setup

Result

Account Hijacking

WhatsApp

WowTalk

EasyTalk

HeyTell

• No verification.

Viber, Forfone, eBuddy XMS

• The authentication mechanisms of Forfone and eBuddy XMS are similar to Viber’s.

Tango, Voypi

• If the number is not registered for the service yet, no verification is done.

• Only if the number is already known to the system, a verification process via SMS is performed.

Sender ID Spoofing

• Other applications use the Extensible Messaging and Presence Protocol (XMPP).

Unrequested SMS

• All examined applications had some kind of timeout that thwarted real mass spamming.

Unrequested SMS (Cont.)

Enumeration

• we selected the US area code 619, which covers the southern half of the city of San Diego, CA and enumerated the entire number range from 000-0000 to 999-9999.

• 21095 valid phone numbers use WhatsApp. (2.5 hours)

Other Vulnerabilities

• WhatsApp

• WowTalk

• Voypi

Conclusion

• Future work might include security assessments of upcoming solutions slated for mass adoption such as Apple’s iMessage.

• Furthermore, research towards an authentication scheme suitable as a best practice template for newly developed applications would be a welcome addition.