MOBILE SECURITY : A Complex Ballgame

The usage of wireless communications, particularly cordless and cellular

phones, has grown dramatically in the past ten years, with the current market

standing at $11 bn. This ability to communicate without being connected to a

stationary phone line has greatly increased the efficiency of corporate,

government, and private sectors. It is estimated that by 2009 there will 2 bn

mobile users around the world. Unfortunately, this has also led to a huge

security problem-the radio signals transmitted and received by these devices can

easily be intercepted, compromised, and exploited.

There are at least three main network types used by cell phones around the

world; the difference in the networks is the frequencies they operate on and the

manner in which the signal is broken up to travel on the frequencies it uses. A

cell phone converts voice into digital and analog signals that are transmitted

by radio frequencies ranging between 800-1,900 MHz.

The transmitting and receiving of radio signals make these devices vulnerable

to electronic threats like eavesdropping and cellular spoofing, and one could

argue that a third threat is the physical loss, damage, or theft of the actual

device.

Electronic eavesdropping can be explained as “listening to or recording of a

cellular call without the permission or knowledge of the calling and/or

receiving party”.

Eavesdroppers do this by using radio frequency scanners and other receiving

equipment to find and listen to the frequencies used by the device. Cellular

phone frequencies are all in the same band range, making it very easy to

intercept these frequencies with electronic scanners.

While communications privacy is a concern, it pales beside the threat of

'cellular spoofing'. Cellular spoofing (also known as cloning) is the process

where a person provides false identification to the cellular communications

provider with the intent to defraud. Eavesdroppers scan the airwaves until they

identify a mobile phone channel, then monitor the transmissions on these

frequencies and wait for an account owner to request a call. For example, the

user sends a voice message like, “operator, this is mobile 1111, may I please

have 456-2345”. The operator would connect the caller and bill mobile account

1111 for the call.

Phreakers (or spoofers) now attempt to detect the MIN and ESN of cellular

phones. They do this by building electrical devices that scan cellular

frequencies and detect the identifier signal that the phone sends back to the

cellular tower. The hacking equipment then strips the MIN and ESN from the

identifier signal. The MIN and ESN are then recorded and programmed into another

cell phone, making it possible for the stolen account to be billed every time

the programmed phone is used.

Innovative Breaches



The idea of sending SMSes (text messages) to crash a mobile phone seemed a

remote possibility until late last year when a Dutch security researcher

revealed that it was possible.

A computer program 'SMS-client' was created to send malformed SMSes from an

Internet-connected PC to a target device. When accepted and modified, the SMS

causes the phone to freeze or shutdown. It was later revealed that a bug in the

phone's software causes the phone to freeze, although Nokia claims to have

created a management tool to fix the problem.

Early this month, a bug was discovered in some models of Siemens. A report

posted on the mobile.box.sk website noted that the Siemens 3568i model (or the

models below) froze whenever it tried to display special characters. The sketchy

report stated that there was a bug in the mobile's display subroutine. The

malformed SMS cannot be removed from the phone without opening it; thus, it will

remain in the phone's memory but can be deleted by a specific computer program

posted on the website.

Counter Measures



A number of government agencies, as well as third parties, infiltrate mobile

networks and record phones calls. However, the GSM Association in October 2002

came up with a new security algorithm, known as A5/3, which provides GSM mobile

phone users with a higher level of protection against eavesdropping. The

security ensures that even if a prospective attacker manages to pull a GSM phone

call out of the radio waves, he will be completely unable to make sense of it,

even if he throws massive computing resources at the task.

The telecommunications industry is designing new high-tech counter measures,

such as digital encryption, to fight the problem. Encryption is a very effective

counter measure that reduces both eavesdropping and spoofing. Another, but not a

very preferable, measure is clipper chip, considering that it does not prevent

criminals from reprogramming the cordless and cellular devices, and also there

is a good chance that the code might get publicly broken, rendering the entire

system useless.

Cell Phone Detectors



'CellPhone Detector Plus' was designed to be portable and user friendly. It

detects radio transmissions and alerts the mobile user to turn off the device.

Batteries or an AC adapter can power it, making it extremely portable. It is

designed to detect mobile phones and two-way radio transmissions in the

continuous frequency range of 400-2000 MHz, including all major communication

formats in use around the world like GSM, CDMA, TDMA, PCS, and two-way radio

handsets. The device has a sensitivity control that can be adjusted to

accommodate coverage areas extending from 2-30 meter outward from the unit,

depending on factors such as physical environment, and strength of the signal

being transmitted by the wireless communication device being detected.

Its advanced features include detection of both analog and digital cell

phones, and a remote alarm output for connection to an external device such as

an alarm system.

The device continuously monitors radio waves emitted by wireless

communication devices, including the short auto-registration signals that cell

phones transmit to the base station whenever the handset is in standby mode, and

upon detection of a transmission, user-selectable alarm(s) get activated.

Apart from the positive attributes of cell phone jammers, they also pose

certain problems. These devices could make the phones unavailable in times of

emergency, could create restrictions in speech, and private property users could

use these devices for personal gains by stopping phone calls and raising

landline call rates.

Dr Amardeep Gupta



The author is HoD, Computer Science, DAV College, Amritsar


vadmail@cybermedia.co.in