UNIVERSITI PUTRA MALAYSIA

FRAUD DETECTION SYSTEM FOR ROTOR PAY PHONE

NURWARDIAH BINTI SPIAN

FK 2007 67

FRAUD DETECTION SYSTEM

FOR ROTOR PAY PHONE

NURWARDIAH BINTI SPIAN

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Master of Science

October 2007

To mak, abah

To my beloved husband

To Tasnim, Aishah and Abdul Rahman

ii

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of

the partial requirements for the degree of Master of Science

FRAUD DETECTION SYSTEM FOR ROTOR PAY PHONE

By

NURWARDIAH BINTI SPIAN

October 2007

Chairman: Samsul Bahari Mohd Noor, PhD

Faculty : Engineering

Pay phone, also known as public telephone, is very vulnerable to fraudulent abuse. Rotor

pay phone is determined as most prone set to fraud. TM Berhad estimates loses millions

of ringgit each year due to fraudulent activities. To help in battling the growing

worldwide problem of pay phone fraud, a fraud detection system was developed.

The system is developed in order to cater many types of frauds, commonly happen to

Rotor pay phone in Malaysia such as line tapping, line cutting, shorting and grounding

fraud. It does not deteriote voice quality of pay telephone or introduces significant delay

during normal pay phone operation such as dialing, conversation and metering signal.

The system comprises of two sets of fraud detection modules; Anti Fraud Device 1

(AFD1) and Anti Fraud Device 2 (AFD2). AFD1 is installed inside pay phone set,

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whereas AFD2 is installed in TM exchange. The system is based on a signal exchange

between AFD1 and AFD2. When the pay phone handset is off-hook, the AFD1 and

AFD2 will communicate with each other to detect any fraud. As soon as fraud is

detected, the line will be terminated by AFD2.

The system has been tested successfully using TM Berhad line infrastructure. The results

obtained shows the system can caters most of pay phones which are located in urban

areas. This will help TM Berhad to greatly reduce loses due to fraud.

iv

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

SISTEM PENGESAN PENIPUAN UNTUK TELEFON AWAM ROTOR

Oleh

NURWARDIAH BINTI SPIAN

Oktober 2007

Pengerusi: Samsul Bahari Mohd Noor, PhD

Fakulti: Kejuruteraan

Telefon bayaran atau dikenali juga sebagai telefon awam, amat terdedah kepada

penipuan. Telefon awam Rotor dikenal pasti sebagai jenis yang paling banyak dan

paling mudah menghadapi masalah ini. TM Berhad telah menganggarkan kerugian

jutaan ringgit setiap tahun kerana aktiviti penipuan yang dilakukan oleh pengguna yang

tidak bertanggungjawab. Jadi, untuk mengatasi masalah yang semakin meningkat bukan

sahaja di Malaysia, malah di seluruh dunia ini, satu sistem yang dapat mengatasi

masalah ini telah dibina.

Sistem ini dibina untuk mengatasi penipuan-penipuan yang sering berlaku kepada

telefon jenis Rotor di Malaysia, seperti penipuan melalui pemintasan talian telefon,

penggantian set telefon, pintasan litar dan pembumian. Sistem ini dibina supaya ia tidak

mengganggu kualiti suara pengguna semasa penggunaan telefon tersebut dan ia juga

v

tidak menyebabkan operasi normal telefon awam terganggu atau menjadi lambat seperti

isyarat panggilan, percakapan dan caj.

Sistem yang dibangunkan ini mempunyai dua modul pengesan penipuan, iaitu Alat Anti

Penipuan 1 (AFD1) dan Alat Anti Penipuan 2 (AFD2). AFD1 dipasang di dalam set

telefon, manakala AFD2 dipasangkan dalam ibusawat TM. Penipuan dapat dikesan

melalui penukaran mesej antara AFD1 dan AFD2. Apabila ganggang telefon diangkat,

AFD1 dan AFD2 akan berhubung antara satu sama lain untuk mengesan penipuan. Jika

penipuan dikenal pasti, talian telefon akan diputuskan oleh AFD2.

Sistem ini telah diuji di makmal. Keputusan yang diperolehi menunjukkan penipuan ke

atas telefon awam jenis Rotor telah berjaya diatasi. Penemuan ini dapat membantu pihak

TM Berhad mengurangkan banyak kerugian yang disebabkan oleh penipuan ini.

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ACKNOWLEDGEMENTS

Project members of Anti-Fraud System for Payphone at TM Research and Development

Sdn Bhd enthusiastically contributed to this project. I am especially indebted to my

Head of Unit CPE and Multimedia Terminal Cluster, Encik Md Azmi Karnain and to my

Technical Assistance, Mazlan Burhanuddin.

I would like to extend a special note of appreciation to my supervisor from Universiti

Putra Malaysia, Dr. Samsul Bahari and co-supervisor, Dr. Hamiruce Marhaban, for their

supervision, advice and guidance.

Words fail to express my thanks to my husband, Haji Mohd Tohir Husin for your

dedication, love and persistent confidence in me. To my parents, Haji Spian Nong Chik

and Hajah Musalmah Bidin who deserve special mention for their inseparable support

and prayers.

Last but not least, I would like to thank everyone though not mention here, but have

contribute in one way or another to the completion of my project. May Allah bless them

all, InsyaAllah.

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I certify that an Examination Committee has met on 26.10.2007 to conduct the final

examination of Nurwardiah Binti Spian on her degree thesis entitled “Fraud Detection

System For Rotor Pay Phone” in accordance with Universiti Pertanian Malaysia

(Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree)

Regulations 1981. The Committee recommends that the candidate be awarded the

relevant degree. Members of the Examination Committee are as follows:

Abd. Rahman Ramli, PhD Professor Madya Faculty of Engineering Universiti Putra Malaysia (Chairman) Mohd. Nizar Hamidon, PhD Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Roslina Sidek, Phd Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Mohd. Fua’ad Hj. Rahmat, Phd Professor Madya Faculty of Electric Engineering Universiti Teknologi Malaysia (External Examiner)

__________________________

HASANAH MOHD ALI, PhD

Professor/Deputy Dean

Faculty of Graduate Studies

Universiti Putra Malaysia

Date: 21 February 2008

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee were as follows:

Samsul Bahari bin Mohd. Noor, PhD Lecturer Faculty of Engineering Universiti Putra Malaysia (Chairman)

Muhammad Hamiruce bin Marhaban, PhD Lecturer Faculty of Engineering Universiti Putra Malaysia (Member)

__________________________

AINI IDERIS, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia

Date: 21 February 2008

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DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions. ____________________________ NURWARDIAH BINTI SPIAN Date: 24 December 2007

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LIST OF TABLES

TABLE Title

Page

2.1

DTMF Signaling Frequencies 2.5

3.1

Functional Decode Table 3.21

xi

LIST OF FIGURES

Figure Title

Page

1.1

System Architecture of Fraud Detection System 1.3

2.1 Rotor Pay phone

2.6

2.2

Operating Environment of AFD 2.13

3.1

AFD1 Block Diagram 3.2

3.2

Pay Phone Line Interface Circuit for AFD1 3.3

3.3

ASK Transceiver Circuit for AFD1 3.5

3.4

PIC16F628A Circuit for AFD1 3.7

3.5

Payment Validation Module Circuit for AFD1

3.9

3.6

AFD1 Process Flow 3.11

3.7

AFD2 Block Diagram 3.13

3.8

Pay Phone Line Interface Circuit for AFD2 3.14

3.9

PIC16F628A Pin Configurations for AFD2 3.15

3.10

ASK Transceiver Circuit Diagram for AFD2 3.18

3.11

DTMF Detector Pin Configuration for AFD2 3.20

3.12

Relay Circuit Diagram for AFD2 3.22

3.13

RS-232 Pin Configuration for AFD2 3.23

3.14

AFD2 Process Flow 3.25

4.1

AFD1 Circuit Board 4.1

4.2

AFD2 Circuit Board 4.2

4.3

AFD1 Circuit Board inside Pay Phone Unit 4.3

4.4

Block Diagram of Testing Setup 4.3

xii

No. Title

Page

4.5

Picture of Testing Setup in Lab Environment 4.4

4.6

DC Voltage of Telephone Line before and after Off-Hook

4.5

4.7

Security Tone Transmitted from AFD1 4.6

4.8

Data Transmission between AFD1 and AFD2 at 0.5 km

4.7

4.9

Data Transmission between AFD1 and AFD2 at 3.5 km

4.8

4.10

Data Transmission between AFD1 and AFD2 at 5.0 km

4.9

4.11

Line Cut-OFF by AFD2 4.10

4.12

Telephone Call without Fraud

4.12

4.13

Telephone Call with Line Cutting Fraud

4.13

4.14 Telephone Call with Line Tapping, Shorting and Grounding Fraud

4.14

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xiv

LIST OF ABBREVIATIONS/NOTATIONS/GLOSSARY OF TERMS

BVI

British Virgin Islands

AWG American Wire Gauge

POTS

Phone On telephone Switching

AC

Attenuating Current

DC

Direct Current

DTMF

Dual Tone Multi Frequency

ROA

Reversal On Answer

CLM

Customer Loop Metering

PNMS

Payphone N Management System

DEL Single Line Phone

PLRZ Polarity Line Reversal

PSTN Public Switched Telephone Network- The part of a Public Telecommunications Network which enables any customer to call and communicate with any other customer either automatically or with operator assistance. A Public Telecommunications Network means a telecommunications network operated by a carrier.

ASK Amplitude Shift Keying

SPM Subscriber Pulse Metering

NRZ Non-Return-to-Zero

LE Local Exchange

FRAM Ferroelectric RAM

CPE Customer Premises Equipment

DTMF

Dual Tone Multi-Frequency

TABLE OF CONTENTS PageDEDICATION iiABSRACT iiiABSTRAK vACKNOWLEDGEMENTS viiAPPROVAL viiiDECLARATION xLIST OF TABLES xiLIST OF FIGURES xiiLIST OF ABBREVIATIONS xiv CHAPTER 1. INTRODUCTION 1.1

1.1 Backgrounds and Motivation 1.1 1.2 System Description 1.3 1.3 Research Objectives 1.4 1.4 Structure of the thesis 1.4

2. LITERATURE REVIEW 2.1 2.1 Introduction 2.1 2.2 Pay Phone System Description

2.2.1 The Phone Line 2.2.2 Bandwidth of Telephone Line 2.2.3 Network Interface 2.2.4 Ringing Signals 2.2.5 Dialing 2.2.6 Line Specification

2.3 Rotor Pay Phone Description

2.1 2.1 2.3 2.3 2.4 2.4 2.5 2.6

2.4 Method of Payphone Fraud 2.102.4.1 Line Tapping 2.4.2 Line Cutting 2.4.3 Shorting 2.4.4 Grounding

2.102.102.102.11

2.5 Current Fraud Detection System 2.5.1 CDR System 2.5.2 Fraud Detection System by Asteria

2.122.122.13

2.6 Other Methods 2.6.1 Call Screening in a Public Telephone Station (United States Patent: 4,794,642)

2.6.2 Method and Apparatus for Preventing Pin Fraud on Coin Telephones That Use Battery Reversal Pulses to Meter

2.162.16

2.17

Charges (United States Patent: 5,757,896) 2.6.3 Apparatus for Conditioning Automatic Coin Validation

Signals, and Method-of-Use Therefor (United States Patent: 6,072,863)

2.6.4 System and Method Therefor of Preventing Fraud an a Pay Phone Credit/Debit Calling Card Authorization (United States Patent: 6,697,472)

2.6.5 Survey of Fraud Detection Techniques 2.6.6 Subscription Fraud Prevention in Telecommunications Using

Fuzzy Rules and Neural Networks 2.6.7 Visualizing Corporate Data

2.18

2.18

2.192.19

2.20 2.7 Conclusions 2.21

3. METHODOLOGY 3.1 Introduction 3.1 3.2 AFD1 Description 3.2

3.2.1 AFD1 Block Diagram Description 3.2 3.2.1.1 Pay Phone Line Interface for AFD1 3.3 3.2.1.2 Amplitude Shift Keying Transceiver for AFD1 3.5 3.2.1.3 Main Controller for AFD1 3.6 3.2.1.4 Payment Validation Module for AFD1 3.9

3.2.2 AFD1 Process Flow 3.113.3 AFD2 Description 3.13

3.3.1 AFD2 Block Diagram Description 3.133.3.1.1 Pay Phone Line Interface for AFD2 3.143.3.1.2 Controller for AFD2 3.153.3.1.3 Ferroelectric RAM 3.163.3.1.4 Amplitude Shift Keying Transceiver for AFD2 3.183.3.1.5 DTMF Receiver for AFD2 3.193.3.1.6 Relay for AFD2 3.223.3.1.7 RS232 Interface for AFD2 3.23

3.3.2 AFD2 Process Flow 3.25 4. RESULT AND DISCUSSION 4.1

4.1 Introduction 4.3 4.2 Testing Setup 4.3 4.3 DC Voltage of Telephone Line Before And After Off-Hook 4.5 4.4 Testing Security Tone From AFD1 To AFD2 4.6 4.5 Testing Data Transmission Between AFD1 and AFD2 For 0.5 km 4.7 4.6 Testing Data Transmission Between AFD1 and AFD2 For 3.5 km 4.8 4.7 Testing Data Transmission Between AFD1 and AFD2 For 5.0 km 4.9 4.8 Testing Line Cut-Off 4.10 4.9 Hyper Terminal Results 4.10

4.9.1 Testing Telephone Call Without Fraud 4.11 4.9.2 Testing With Line Cutting Fraud 4.13 4.9.3 Testing With Line Tapping/Shorting/Grounding Fraud 4.14

5. CONCLUSION AND FUTURE RECOMMENDATION 5.1 5.1 Conclusion 5.1 5.2 Recommendation 5.2

REFERENCES R.1 APPENDICES A.1 BIODATA OF THE AUTHOR B.1

CHAPTER 1

INTRODUCTION

1.1 Background and Motivation

Pay phone is a public telephone, enables a person to make phone call without requiring

the person to be a subscriber to a particular telephone network service provider. Pay

phone requires the use an immediate payment in order to make a call from it. A user

inserts either the required value for a telephone call in coins or a card representing a call

value that can be read by the telephone into a phone to make a phone call.

Pay phones are usually found in public places such as street corners, outside of

convenience markets, bus and airport terminals, and shopping malls. Although it is not

as frequent, they may also be found in private businesses and homes. This privately

operated pay phone, not operated by the telephone network provider, are installed by a

private operator at a desired site and connected to the pay phone exchange via a service

which accepts all outgoing calls. The private operator pays the lease on this connection

and recoups the money from the users of the phone by collecting the payment through

coins or telephone card.

There are situations where the pay phone or pay phone connection may be used

dishonestly to make calls without providing the appropriate payment. Cable and

Wireless General Manager Mr. Vance Lewis described the pay phones as one of the

most convenient and popular ways of communicating in the BVI, which means the

system is easily vandalized and or fraud [1].

1.1

There are several ways that a pay phone could be fraudulently used such as through

tampering or vandalism of pay phone to enable calls to be made without providing the

correct payment. For example card readers can be short circuited to enable calls to be

made without payment. Other methods of fraud involve bypassing the pay phone itself,

such as by tapping into the pay phone line to bypass the pay phone, using a normal

phone or replacing the pay phone with a normal telephone. As the telephone exchange

accepts all calls from the line connecting the pay phone, any call using that line will be

accepted, whether the appropriate fee is paid by the user or not.

In this project, a fraud detection system is invented to prevent fraud in pay phones that

provides equipment within the pay phone to monitor the dial tone and prevent further

calls being made without appropriate payment. The fraud detection system is limited to

Rotor pay phone since it has been found that this type of pay phone are the most

susceptible to allowing users to make unauthorized call without payment by using

tapping or cutting phone line, shorting and grounding the pay phone electronic main

board by pin and inducement of current surges [2]. This is due to the mechanical design

of the pay phone which makes users easy to do fraud [3].

1.2

1.2 System Description

Public Switching Telephone Network ( )

Figure 1.1: System Architecture of Fraud Detection System

The block diagram of a fraud detection system for pay phone is shown in Figure 1.1.

The system comprises of two sets of fraud detection modules; Anti Fraud Detection 1

(AFD1) and Anti Fraud Detection 2 (AFD2). AFD1 is installed inside pay phone set,

whereas AFD2 is installed in TM Exchange. These modules are connected to each other

through Public Switching Telephone Network (PSTN). The system is based on a signal

exchange between AFD1 and AFD2. The data exchange takes place on reception of each

metering pulse or in particular cases during the phone call. The data, if correct, is

interpreted by the AFD2 as presence of a pay phone connected to that telephone line and

as confirmation of metering. If this data is missing or incorrect, the AFD2 will open the

line immediately, interrupting the current call. If data received is correct, AFD2 will

check the first 2 digits numbers. If the numbers are ‘99’, or other free call numbers that

has been set, it will be disabled. If other than free call number detected, AFD2 will wait

for AFD1 to send security data signal every 1 minutes. If no coins or card value is

detected, AFD2 will terminate the line.

1.3

1.4

1.3 Research Objectives

The main objective of this work is to conduct a study, design and to develop a system

that caters fraud problems in pay phone, installed by TM Berhad, such as line tapping,

line cutting, shorting and grounding fraud. This project involves testing using Rotor pay

phone, as one of the most prone set to fraud [2], [3]. The design should cater the current

fraud detection system problem that introduces significant delay during normal pay

phone operation (dialing, conversation and metering signal). The design also should be

able to cater for pay phones which are located in urban areas.

1.4 Structure of the Thesis

The thesis is organized into five chapters and 13 appendices. The areas covered in each

chapter are detailed in the following sections. The first chapter introduces the subject of

the thesis and describes its organization. Chapter two reviews the literature on the

background information of pay phone system and Rotor-type pay phone system. Then,

methods of fraud commonly happen to pay phone system are described in detail.

Readers will understand how users can do fraud to pay phone. Current fraud detection

systems are described to show where the idea to develop this fraud detection system is

generated. Chapter three describes the design of hardware and software of AFD1 and

AFD2. In chapter four the fraud detection system was implemented and tested in the

laboratory. The experimental results and discussions are also presented. Finally, chapter

five entails conclusion drawn from this work and recommendations for future studies.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

The purpose of an anti-fraud system for rotor type pay phone is to cancel frauds

commonly happen to rotor type pay phone. Common frauds that have been recognized

currently are line tapping, pay phone replacement with normal phone or line cutting, pin

fraud and piezo fraud. This chapter describes pay phone system, fraud description and

current fraud detection system.

2.2 Pay phone System Description

This section describes pay phone system specifications in details.

2.2.1 The Phone Line

A pay phone is usually connected to the telephone exchange by about three miles or 4.3

km of a twisted pair of No.22 American Wire Gauge (AWG) or 0.5mm copper wires,

known by Phone Company as “the loop”. Although copper is a good conductor, it does

have resistance. The resistance of No. 22 AWG wire is 16.46 Ohms per thousand feet at

77oF (25oC). Wire resistance usually expressed as Ohms per kilometer.

Because pay phone apparatus is generally considered to be current driven, all pay phone

measurements refer to current consumption, not voltage. The length of the wire

connecting the subscriber to the telephone exchange affects the total amount of current

that can be drawn by anything attached at the subscriber’s end of the line.

2.1

The voltage applied to the line to drive the telephone is 48 VDC. Pay phone is peculiar

in that the signal line also the power supply line. The voltage is supplied by lead acid

cells, thus assuring a hum-free supply and complete independence from the electric

company, which may be especially useful during power outages.

At the telephone exchange, the DC voltage and audio signal are separated by directing

the audio signal through 2uF capacitors and blocking the audio from the power supply

with a 5 H choke in each line. Usually these two chokes are the coil windings of a relay

that switches the phone line at the exchange. The resistance of each of these chokes is

200 Ω.

During on-hook or not in-use, the DC resistance of telephone line should be about 10

MΩ, and it should draw not more than 5 μA while phone is in this state. When the phone

is in use, or off-hook, current drawn to power the phone is between 15 mA to 90 mA.

The phone line has impedance, composed of distributed resistance, capacitance and

inductance. The impedance will vary according to the length of the loop, the type of

insulation of the wire, and whether the wire is aerial cable, buried cable, or bare parallel

wires strung on telephone poles. The impedance is normally assumed to be 600 Ω to 900

Ω.

2.2

2.2.2 Bandwidth of the Telephone Line

A Phone on Telephone Switching (POTS) line has a bandwidth of 3 kHz. A normal

POTS line can transfer the frequencies between 400 Hz to 3.4 kHz. The frequency

response is limited by the telephone transmission system components; transformers and

capacitors. Other reason to drop out the lowest frequencies is to keep the possibly strong

mains frequency (50 or 60 Hz and its harmonic) humming away from the audio signal

we can hear.

2.2.3 Network Interface

The telephone has a circuit called network interface (also called voice network or

telephone hybrid) which connects the microphone and speaker to the telephone line.

Network interface circuitry is designed so that it sends only the current changes the other

telephone causes to the speaker. The current changes which the telephone’s own

microphone generates are not sent to the speaker. All this is accomplished using quite

ingenious transformer circuitry. In theory, the hybrid circuit can separate all incoming

audio from the audio sent out at the same time if all the impedances in the circuitry

(hybrids on both ends and the wire impedance between) are well matched.

Unfortunately, the hybrid is by its very nature a “leaky” device. As voice signals pass

from the 4-wire to the 2-wire portion of the network, the higher energy level in the 4-

wire section is also reflected back on itself, creating the echoed speech. Since the circuit

does not work perfectly, own voice in the speaker still can be heard. The actual amount

of signal which is reflected back depends on how well the balance circuit of the hybrid

matches the 2-wire line. This has an advantage; some people who use the telephone

prefer to hear some of their own voice back. This effect is called ‘side tone’ and gives

2.3