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Introduction
What is Bypass fraud?
A call via a legitimate path/route will be bypassed so that there
is a revenue loss.1 Generally for making national or international
calls, rates are xed by regulators in a country or by an individual
or group of operators. Bypass fraud is prevalent in countries where
there is a difference in rates between the retail calling, national calling
and international calling. Moreover in some countries, international
gateways are monopolized by government operators. The fraudsters
make use of difference in rates and ensure that there are enough prots
for them and serve as the key motivating factor to invest in procuring
the equipments and GSM connections for conducting a large scale
Bypass fraud. In countries where the international to national
terminating charge margins are low, nil or negative, the bypass fraud
either does not exists or is conducted a very low scale. It is one of the
latest and most severe threats to a telecom operator’s revenue. It is an
unauthorized exploitation or manipulation of an operator’s network.
This can happen in two ways:
i. SIM Box Interconnect Fraud
ii. GSM Gateway Fraud
Such methods make fraudsters gain incentives to evade such high
tariff interconnects and deliver costly international calls illicitly.
Fraudsters use Voice over Protocol – Global System for Mobile
Communications (VOIP-GSM) gateways also called as “SIM Boxes”,
which are used to receive incoming calls (via wired connections) and
deliver them to a cellular voice network. It appears as if it is through
a local call appearing from a customer’s phone. This practice not
only dramatically degrades the network experience for legitimate
customers violating the telecommunication laws in many countries
but also extremely protable for simboxers/fraudsters resulting in
revenue loss signicantly.2
Cellular networks
Commonly used standard for implementing cellular
communication is a set of Global System for Mobile Communication
(GSM). Majority of countries such as United States, Europe, Africa
and Asia use GSM for mobile communication and is popularly called
as 2G cellular networks and subsequently evolved into Universal
Mobile Telecommunications Service (UMTS-3G) and Long Term
Evolution(LTE-4G). A smart card called Subscriber Identity Module
(SIM) is being used by GSM and it manages the SIM card that
carries the identity and placed on any device authorized to operate
on a carrier’s. Every communication transaction in network is
cryptographically authenticated. SIM cloning was prevalent in the
recent past which negated guarantee of specic SIM card attribution.
Latest advanced technology SIM cards have hardware security
and practical key recovery protections that prevents card cloning.
Additionally, GSM standards uses audio codec called GSM Full-
Rate (GSM-FR) which is also frequently implemented in Voice over
Internet Protocol (VOIP) software.3
Voice over internet protocol
Voice over Internet Protocol (Voice over IP, VoIP and IP telephony)
is a methodology and group of technologies for the delivery
of voice communications and multimedia sessions over Internet
Protocol (IP) networks, such as the Internet. The terms Internet
telephony, broadband telephony, and broadband phone service
specically refer to the provisioning of communications services
(voice, fax, SMS, voice-messaging) over the public Internet, rather
than via the public switched telephone network (PSTN). There are
two ways in which clients can complete a VoIP call. Firstly, a call
can be completed exclusively using internet; secondly calls might
also be routed from/to a VoIP client to a Public Switching Telephone
Network (PSTN) through a VoIP gateway. The transport is similar to
traditional telephony network. It uses special media codec’s protocol
to encode audio and video. Popular VoIP providers are Skype, Vonage
and Google which uses both IP-only and IP-PSTN calls. Step by step
process for a VoIP is given below:
i. VoIP calls are setup using text based protocol called as Session
Initiation Protocol (SIP).
Forensic Res Criminol Int J. 2019;7(1):31‒35. 31
© 2019 Kala. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and build upon your work non-commercially.
A study on internet bypass fraud: national security
threat
Volume 7 Issue 1 - 2019
Kala N
Assistant Professor &Director, Centre for Cyber Forensics and
Information Security, University of Madras, India
Correspondence: Kala N, Assistant Professor &Director,
Centre for Cyber Forensics and Information Security, University
of Madras, Chennai- 600 005, India, Email
Received: October 25, 2018 | Published: February 06, 2019
Abstract
Internet bypass fraud is one of the most complicated fraud types in the recent times.
Telecom regulators and mobile operators face a staggering revenue loss since bypass
fraud is proving to be the most prolific and costly frauds. The gateway equipments
such as fixed, Voice over Internet Protocol(VoIP), Global System for Mobile
communication(GSM), Code Division Multiple Access (CDMA), VOIP to GSM, fixed
line gateway are used to terminate international inbound calls to local subscribers by
deviating traffic away from legal interconnect gateways. Operators sending outbound
international traffic connect to interconnect operators with lower rates, leading to
termination of network operator’s loss of revenue. Bypass fraud is considered illegal
since those who undertake it are not licensed to provide telecommunication services.
Bypass fraud is also considered as a national security threat since terrorist groups use
this device to make calls which appears to be a local call. This paper focuses on the
study of bypass fraud as a National security threat. Further this study also suggests the
methods for mitigating such security threat.
Forensic Research & Criminology International Journal
Review Article Open Access
A study on internet bypass fraud: national security threat 32
Copyright:
©2019 Kala
Citation: Kala N. A study on internet bypass fraud: national security threat. Forensic Res Criminol Int J. 2019;7(1):31‒35. DOI: 10.15406/frcij.2019.07.00262
ii. SIP function is to establish which audio codec will be used for
the call.
iii. Once a call connection has been established audio ows
between the callers
iv. It uses Realtime Transport protocol (RTP) for this purpose
v. This is typically carried over User Datagram Protocol (UDP)
vi. There are many codec’s are mandatory, although some are
optional.
vii. When GSM-FR is implemented outside of cellular network and
sometimes used by VoIP software.
Simbox
Simbox is a device used as part of a VoIP gateway installation.
It contains a number of SIM cards, which are linked to the gateway
but housed and stored separately from it. A SIM box can have SIM
cards of different mobile operators installed, permitting it to operate
with several GSM gateways located in different places. The SIM box
operator can route international calls through the VoIP connection and
connect the call as local trafc, allowing the box’s operator to bypass
international rates and often undercut prices charged by local mobile
network operator’s that connects VoIP calls to GSM voice network.
It does not use data network. Simbox device requires one or more
SIM cards to wirelessly connect VoIP call to GSM network. A Simbox
acts as a VoIP client whose audio input and output are connected to a
Mobile Phone. These devices have strong market in private enterprise
telephone networks. Such private enterprise use GSM gateways with
the permission of the licensed telecommunications provider and this
causes to tariff reduction enabling them to pay often at lower cost
for terminating a call. However, this is possible and legal only for
domestic calls. It is enabled by Voice over Internet Protocol (VOIP)
Global System for Mobile Communication (GSM). The equipment
is called SIM Boxes and the same is illustrated in Figure 1. In this
process Simboxing connects the VOIP calls to a local cellular voice
network through a collection of SIM cards and cellular radios. In
a normal course the calls will be received by the network service
provider and call tariffs will be charged. In Simboxing, calls will
bypass the normal course of connection, appearing to originate from
customer phone, to a network provider. The calls are delivered at a
subsidized domestic rate instead or international rate. Such an activity
has its negative impact availability, reliability and quality of service
for legitimate consumers. Moreover, it also creates network hotspots
by injecting huge volume of tunneled calls, thereby causing revenue
loss to network operators.
Figure 1 Simbox.
Interconnect bypass fraud using simboxing
Most common implementation of interconnect bypass fraud4 is
known as SIM Boxing. Fraudsters use simbox bypass the international
calls and make it appear as if it is a domestic call causing revenue loss
to telecom operators. There is a high demand for GSM-VoIP gateways
spanning a wide range of features; numbers of concurrent calls are
supported. Some of them have only limited functionality, while
others hold several simcards and also supports a variety of audio
codecs in a “SIM server”. Sometimes one or more radio interfaces
calls using the “Virtual SIM cards” from the server. This prevents
location based fraud detection. Miscreants, utilize this and commits
the fraud. The cost of simbox equipment goes upto 200,000 USD. A
typical international call which is routed through a regulated licensed
interconnect is illustrated in the Figure 2. Let us assume client A is
located in India and client B is located in UK. In a typical call, when
client A is calling client B, the call is routed through the telephone
network in India (labeled as “Foreign PSTN core”) to an interconnect
between client A and client B network in UK. This passes through
client B’s domestic network (labeled as “Domestic PSTN Core”) and
communication establishes between client A and client B. If client
A and client B are not in neighboring countries, there can be many
interconnects and intermediary networks. This is very critical the
connections are heavily monitored for billing purpose and quality.
It can be seen that VoIP calls initiated from services such as Skype
that terminates on a mobile phone also passes through regulated
interconnect. A Simbox call is represented in Figure 3. A Simboxed
international call avoids regulated interconnect by routing the call to a
Simbox which completes the call using the local cellular network. In
a simbox case, client A call is routed through domestic network, but
instead of passing through the regulated interconnect, the call is routed
over internet protocol (VoIP) to simbox in the destination country. In
doing so, the simbox places a separate call on the cellular network
in the destination country, then routes the audio from IP call into the
cellular call, which is routed to client B through the domestic network.
The same is illustrated in Figure 3. The main disadvantage here is
neither of end users is aware that the call is being routed through a
simbox. This causes a contractual breach of trust between two Internet
Service Providers (ISPs) who have agreed to route trafc between
their networks. The intermediaries own prot from reduced prices.
Two types of attack can take place. Firstly, hijacking of international
call; secondly, hijacking and re-injecting of an international call.
First type has been described above. In the second type, Simboxes
re-inject telecom voice trafc into the mobile network masked as
mobile customers and operator has to pay for the re-injected calls.5 In
general there are three types of routes that are used in communication
networks. They are:
i. White Route: both source and destination have legal
termination.
A study on internet bypass fraud: national security threat 33
Copyright:
©2019 Kala
Citation: Kala N. A study on internet bypass fraud: national security threat. Forensic Res Criminol Int J. 2019;7(1):31‒35. DOI: 10.15406/frcij.2019.07.00262
ii. Black Route: both source and destination have illegal
termination.
iii. Grey Route: the termination is legal for one entity or country,
but illegal for the other end.
Figure 2 Typical international call routed through regulated licensed interconnect.4
Figure 3 A Sim box international call.4
GSM gateway interconnect devices
Interconnect systems, such as gateways, allows voice
interoperability between otherwise incompatible radio communications
systems. Interoperability is achieved by retransmitting voice over
interconnected radio subscriber both mobile as well as portable
units. Linking incompatible radio frequency bands and systems can
be relatively easy and effective. Interconnect deployment requires
a new strategy and operational procedures. The gateway approach
to interoperability has signicant potential, considering the ease of
gateway deployment and relatively low cost when compared to wide
area radio system. A gateway is a type of interconnect system. They
can also connect trunked talk groups, encrypted networks, public
telephone systems, and cellular or satellite phone connections. Most
gateway devices are mobile and portable, but many are used in
permanent congurations.6
Interconnect bypass fraud global scenario
According to a survey conducted by Communication Fraud Control
Association (CFCA), in the year 2015, the revenue loss amounts to
$3.77 Billion USD. According to this survey, top 10 countries where
the fraudulent calls originated, is listed in Table 1. Further survey
points out the percentage of top ve frauds, in which interconnect
Bypass fraud in network is around 5%, whereas in roaming status,
interconnect bypass fraud amounts between 20 – 25%. This can be
seen evidently from the following Figure 4. Authorities in US say that
the hackers were involved in an international crime ring that scammed
telecommunication companies out of an estimated $50million USD
in last few years. FBI most wanted list of cyber criminals have
been arrested by authorities in their native Pakistan. Serbian Police
cracks down on illegal SIM Box Scheme. According to Serbia’s
interior Ministry in cooperation with the special department of cyber
crime of Prosecutor’s Ofce and the Ministry of Interior Macedonia
have identied miscreats using Simboxes to bypass international
communications via VoIP and making low-cost calls in Serbia. More
than 40,000 SIM cards were found in Macedonia of mobile operators
from Serbia, Croatia, Slovenia, Albania, Bosnia and Herzegovina.
There are incidents in Ghana where the fraudsters connived with
partners abroad to route internet calls via VoIP to make it appear as
if the call is a local one. Even. The seized Simcards and connecting
devices are illustrated in Figure 5. There has been incidence where
even women have been arrested for alleged simbox fraud.7
Table 1 Country wise fraudulent calls in percentage based on call origin.
Countries Fraudulent calls percentage
United states 5%
Pakistan 4%
Spain 4%
Cuba 3%
Italy 3%
Philippines 3%
Somalia 3%
United Kingdom 2%
Dominican Republic 1%
Egypt 1%
Figure 4 Seized sim cards and simbox.
A study on internet bypass fraud: national security threat 34
Copyright:
©2019 Kala
Citation: Kala N. A study on internet bypass fraud: national security threat. Forensic Res Criminol Int J. 2019;7(1):31‒35. DOI: 10.15406/frcij.2019.07.00262
Figure 5 Percentage comparison of Simbox fraud in network vs. roaming.5
Interconnect bypass fraud Indian scenario
Recently, in India, a techie has been arrested for operating
telephone exchange for a Pakistan spy. According to the sources the
Uttar Pradesh8 Anti-Terrorism squad have busted an illegal telephone
exchange and spying racket causing national security threat. This act
has been committed by a software engineer from south Delhi and ten
others from Lucknow and other parts of UP. The exchanges were not
only making lakhs of rupees by routing international calls bypassing
the legal gateways. These systems were used for Pakistan’s Inter-
Service Intelligence (ISI) to call Army ofcials to elicit information
from them. The racket was busted after the defence ministry and
Army alerted the military intelligence in Jammu & Kashmir. ISI has
been spying over and innocent victims have been sharing information.
Intelligence ofcials unearthed the racket and found illegal network
was using Simbox to carry out their spying activities. The callers
based in Pakistan, Bangladesh made calls using VoIP through Simbox
and connected to receivers in India. The receivers in India could only
see Indian numbers on their phone screens. The law enforcement
authorities have recovered 16 SIM BOX units, 140 prepaid cards,
10 mobile phone and 28 data cards and ve laptops. The SIM Box
recovered from the suspects is illustrated in Figure 6.
Figure 6 Simbox recovered from Accused.5
Countermeasures for interconnect bypass
fraud
Most common approaches to detect Bypass fraud are:
i. Bypass route detection through call generation
ii. Simbox detection using Fraud Management systems (FMS)
iii. Unusual ows and volumes
iv. Unusual called number spreads
v. A-typical trafc peaks for on-net trafc
vi. Many SIM card identities (IMSIs) to a single equipment
identity (IMEI)
vii. Use of only one cell site
viii. An absence of SMS, data or roaming service use
Hybrid analysis: Call generation providers and FMS tools
providers collaborate to pool their alerts in order to more efciently
detect the characteristics described above.
i. Network trafc analysis
ii. Call Data Record (CDR) Analysis
iii. Features extracted from CDR data are utilized to build a
decision tree that can be used to distinguish between legitimate
and Simbox accounts.
Features include: total number of outgoing calls, incoming calls,
number of SMS originating and SMS terminating, total number of
hand over and the total number of different location.9
Ammit
Simbox detection tool focuses on loss rate and simbox codec.
Moreover, simbox detection based on measurable differences
between true GSM and tunneled VoIP audio. Ammit is the rst system
to combat simboxing using call audio.10
Mocean simbox detector
The detection of Simbox tracks the calls based on caller line
identication.11
Statistical proling system
Identication based on monitoring complex call patterns including
outgoing call count, distinct destinations ratio, cell sites used,
incoming to outgoing call ratio and so on. It is also called statistical
proling based detection. Other type of detection mocean Simbox
detector which has capabilities to distinguish between the normal
international call trafc path and simbox bypass international trafc
path.
A study on internet bypass fraud: national security threat 35
Copyright:
©2019 Kala
Citation: Kala N. A study on internet bypass fraud: national security threat. Forensic Res Criminol Int J. 2019;7(1):31‒35. DOI: 10.15406/frcij.2019.07.00262
Fraud management system (FMS)
FMS system includes the following detection systems:
i. Trafc analysis
ii. International Mobile Subscriber Identity (IMSI) number/
Integrated Circuit Card ID (ICCID) series analysis
iii. International Mobile Equipment Identity number.12
Conclusion
Telecommunication networks in developing nations rely upon
the tariffs collected through regulated licensed interconnects in order
to subsidize the cost of their deployment and operation. Fraudsters
Bypass the legal connection and commit fraudulent activity using
simboxes by tunneling trafc from VoIP connection into a genuine
network unauthorized way. In this study an attempt has been made to
identify the different ways interconnect bypass occurs. Further, this
study has also identied the different devices used to commit such
fraudulent activity. Moreover, a comparison between the current
scenario from global perspective and Indian perspective has been
made. Focus has been made to identify how the antisocial element
and miscreants use such methodology and cause a national security
threat across the globe. Finally, different fraud management systems
that are currently in vogue have been discussed.13
Acknowledgments
None
Conicts of interest
The author declares that there are no conicts of interest.
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