Research Reveals Collision of Cell Networks With Internet

In the light of Apple’s iPhone release, mobile malware hacking seems to have picked up again. While most prominent research topics are on client exploits (iPhone hacking, mobile malware, etc.) and messaging (SMS phishing, spamming, etc.), there are some other interesting mobile research topics that are worth a look.

One of the trends we have seen in the past year is that cellular mobile networks are incorporating themselves with the Internet. The iPhone, for example, encourages application developers to write browser-based applications using the Internet. Service providers are also rapidly deploying 3G networks throughout the world for faster Internet mobile services. As we know, when combining two different networks with different threat models, the end result might not be secure.

Several works in the academic area have pointed this out, and some have successfully exploited the cellular network via the Internet to cause a denial of service. Penn state’s paper used SMS, which can be sent freely on the Internet, to cause DoS on the cellular network. They exploit the fact that cellular networks, when sending SMS, use the same, narrow bandwidth control channel as phone calls. By flooding a service area with SMS messages, they can effectively block incoming and outgoing phone calls. UC Davis’ paper, on the other hand, used MMS to cause DoS on the host. They discovered that an outside server can obtain information from MMS messages from mobile devices, and attackers can use this information to send rogue packets to the phone, causing the battery life to decrease significantly. Furthermore, Sprint’s and Penn State’s papers further discuss the vulnerabilities on the cellular network that makes these attacks possible.

In addition, initial research from the cellular network against Internet traffic has emerged. A paper from Sprint outlines how a phone can manipulate the cellular network’s base station scheduler such that it will provide an unfair advantage to the attacker. In EV-DO networks, the base station is responsible for allocating time slots for competing mobile devices to transmit. The scheduler used in EV-DO is “proportional fair,” which calculates a score for each mobile device per time slot based mainly on their signal strength. Because the base station relies on each phone’s reported signal strength to assign time slots for each mobile phone to transmit, the mobile devices can manipulate their signal strength in such a way that could “starve” other users of timeslots.

These works, though research oriented, are very interesting. They take a new approach to looking at the cellular network–in a way that wasn’t obvious before Internet integration.