Technical Field of the Invention

The invention relates to a method and apparatus for use in a communications network, and in particular relates to a method and apparatus for detecting whether a fixed- line/landline telephone number has an active call forwarding condition, i.e. a condition that means a telephone call to the fixed-line/landline telephone number will be diverted or re-directed to another telephone number.

Background to the Invention

The occurrence of banking and credit card transactions over the Internet is rapidly increasing in many countries, including the UK. In order to try and ensure that these transactions are secure, many financial institutions use a two factor authentication approach to verify that a transaction is being made by the account holder and not a fraudster that has stolen the account holder's identity.

The identity can be stolen in various ways, a typical one being a phishing attack on the computer of an account holder, which can trick the account holder into providing identity information and challenge-responses to the fraudster. The fraudster can use these details to imitate the account holder and initiate a transaction from the account holder's account or using their credit card details. To counter this, a second authentication factor can be used in which a telephone call is placed to a mobile or fixed-line (also known as landline) telephone number specified by the account holder to verify that the transaction is genuine. This mobile telephone number (i.e. a number associated with a mobile telephone subscriber) or fixed-line telephone number (i.e. a number associated with a fixed-line connection to a specific address/location) will have been specified by the account holder prior to the transaction, e.g. when they opened the account and provided their personal details to the financial institution. Information may be exchanged between the account holder and financial institution during this verification telephone call. For example the account holder may be asked to enter a code into the computer that the financial institution provides to the account holder during the call, or the account holder can enter a code displayed on the computer into the telephone keypad. However, fraudsters have devised ways to divert telephone calls made to the account holder's telephone number to a telephone managed by themselves, thereby enabling them to complete the fraudulent transaction without the account holder being alerted. These methods can be applied to the account holder's telephone number regardless of whether the number is a mobile number or a fixed-line number. The number to which the fraudsters divert the telephone call from the account holder's telephone number is typically a mobile number, since that does not have a fixed and easily trackable location, although in some cases the fraudsters may divert the telephone call to a fixed telephone number (perhaps in a different country).

If the fraudster can set up this divert on the account holder's telephone number without being detected (at least by either the calling party or the called party) then this obviously has a severe impact on the security of many transactions and leads to significant losses for the financial institutions involved.

Techniques are available for allowing a calling party (i.e. the party initiating a telephone call, e.g. a financial institution) to detect when there is an active call forwarding condition on a mobile telephone number of a called party (i.e. a condition that means a telephone call to the mobile telephone number of the called party will be diverted or redirected to another mobile or fixed telephone number that belongs to the called party or a third party (e.g. fraudster)), and these techniques can be used by the financial institutions (the calling party) to detect this call forwarding condition and determine whether to continue with the requested transaction.

In the UK, there are a number of different providers of fixed-line telephone services, and they use a variety of legacy switching systems and newer technologies to provide a telephone service. The situation is similar in many other countries. Although the legacy switching systems may provide a call forwarding service to their customers (i.e. a service whereby a telephone call to a first telephone number can be automatically diverted to a second telephone number), when a call forwarding service referred to in some cases as Unconditional Call Forwarding is active, the notification of this service being active (i.e. an active call forwarding condition) is not carried back towards the calling party (i.e. the originator of the telephone call) over the signalling protocol used, either to the calling party themselves, or even to the originating switch, and there is no reliable technique available that allows a calling party to detect when there is an active call forwarding condition on a fixed (landline) telephone number of a called party in these types of networks. Unconditional Call Forwarding is also undetectable to the subscriber/customer for which the call forwarding is active (unlike in other types of forwarding where it may be apparent to the subscriber/customer, for example when they pick up the handset of their telephone and hear a modified dialling tone).

Therefore, there is a need for a method and apparatus for detecting whether a fixed- line/landline telephone number has an active call forwarding condition, so that, for example, financial institutions can check during authentication of account or credit card transactions that they are communicating with someone on a registered telephone number. Summary of the Invention

According to a first aspect of the invention, there is provided a method of detecting whether a first fixed-line telephone number has an active call forwarding condition, the method comprising monitoring the signals received in the set up of a telephone call to the first fixed-line telephone number; and detecting whether the first fixed-line telephone number has an active call forwarding condition based on the timing of signals received in the set up of the telephone call to the first fixed-line telephone number and/or the sequence in which signals are received in the set up of the telephone call to the first fixed-line telephone number. In some embodiments the step of monitoring the signals comprises monitoring the signals received in the set up of the telephone call for a first type of signal and a second type of signal.

In some embodiments, the step of detecting whether the first fixed-line telephone number has an active call forwarding condition comprises determining the time period from receipt of a first signal of the first type of signal to the time of receipt of a signal of the second type and/or the sequence in which a signal or signals of the first type of signal and a signal of the second type of signal are received. In some embodiments, the step of detecting whether the first fixed-line telephone number has an active call forwarding condition comprises determining the sequence in which the a signal or signals of the first type of signal and a signal of the second type of signal are received and detecting that the first fixed-line telephone number has an active call forwarding condition if a signal of the first type is received after a signal of the second type.

In some embodiments, the step of detecting whether the first fixed-line telephone number has an active call forwarding condition comprises determining the time period from receipt of a first signal of the first type of signal to the time of receipt of a signal of the second type and detecting that the first fixed-line telephone number has an active call forwarding condition if the time period is greater than a threshold value.

In some embodiments, the threshold value is equal to or less than 2000ms, 1750ms or 1500ms. In some embodiments the threshold value is equal to or greater than 1000ms, 1250ms or 1500ms. In some embodiments, the threshold value is 1500ms. In some embodiments, the threshold is a value in the range 1000ms-1500ms.

In some embodiments, the first type of signal is an Additional Call Information, ACI, message and the second type of signal is an Address Complete Message, ACM. In some embodiments, the method further comprises the steps of determining whether there are System-X switches in the communication network hosting the first telephone number; and if there are System-X switches in the communication network, detecting whether the first fixed-line telephone number has an active call forwarding condition at least based on the sequence in which signals are received in the set up of the telephone call to the first fixed-line telephone number; and otherwise detecting whether the first fixed-line telephone number has an active call forwarding condition based on the timing of signals received in the set up of the telephone call to the first fixed-line telephone number. In some embodiments, the method further comprises the steps of ending the telephone call to the first fixed-line telephone number before the call is answered; and sending an indication of whether an active call forwarding condition has been detected to another party. In other embodiments, the method further comprises the steps of ending the telephone call to the first fixed-line telephone number if an active call forwarding condition is detected; and continuing with the telephone call to the first fixed-line telephone number if an active call forwarding condition is not detected.

According to a second aspect, there is provided a computer program product having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processing unit, the computer or processing unit is configured to perform any of the methods described above. According to a third aspect, there is provided an apparatus for use in a communication network for detecting whether a first fixed-line telephone number has an active call forwarding condition, the apparatus comprising a signalling interface for receiving signals sent in the set up of a telephone call to the first fixed-line telephone number; and a processing unit that is configured to monitor the signals received in the set up of the telephone call to the first fixed-line telephone number; and to detect whether the first fixed-line telephone number has an active call forwarding condition based on the timing of signals received in the set up of the telephone call to the first fixed-line telephone number and/or the sequence in which signals are received in the set up of the telephone call to the first fixed-line telephone number.

In some embodiments, the processing unit is configured to monitor the signals received in the set up of the telephone call for a first type of signal and a second type of signal.

In some embodiments, the processing unit is configured to detect whether the first fixed-line telephone number has an active call forwarding condition by determining the time period from receipt of a first signal of the first type of signal to the time of receipt of a signal of the second type and/or the sequence in which a signal or signals of the first type of signal and a signal of the second type of signal are received. In some embodiments, the processing unit is configured to detect whether the first fixed-line telephone number has an active call forwarding condition by determining the sequence in which the a signal or signals of the first type of signal and a signal of the second type of signal are received and detecting that the first fixed-line telephone number has an active call forwarding condition if a signal of the first type is received after a signal of the second type. In some embodiments, the processing unit is configured to detect whether the first fixed-line telephone number has an active call forwarding condition by determining the time period from receipt of a first signal of the first type of signal to the time of receipt of a signal of the second type and detecting that the first fixed-line telephone number has an active call forwarding condition if the time period is greater than a threshold value.

In some embodiments the threshold value is equal to or less than 2000ms, 1750ms or 1500ms. In some embodiments the threshold value is equal to or greater than 1000ms, 1250ms or 1500ms. In some embodiments, the threshold value is 1500ms. In some embodiments, the threshold is a value in the range 1000ms-1500ms.

In some embodiments, the first type of signal is an Additional Call Information, ACI, message and the second type of signal is an Address Complete Message, ACM. In some embodiments, the processing unit is configured to determine whether there are System-X switches in the communication network hosting the first telephone number; and to detect whether the first fixed-line telephone number has an active call forwarding condition at least based on the sequence in which signals are received in the set up of the telephone call to the first fixed-line telephone number if it is determined that there are System-X switches in the communication network; and to detect whether the first fixed-line telephone number has an active call forwarding condition based on the timing of signals received in the set up of the telephone call to the first fixed-line telephone number if it is not determined that there are System-X switches in the communication network.

In some embodiments, the processing unit is configured to end the telephone call to the first fixed-line telephone number before the call is answered; and to send an indication of whether an active call forwarding condition has been detected to another party.

In other embodiments, the processing unit is configured to end the telephone call to the first fixed-line telephone number if an active call forwarding condition is detected; and to continue with the telephone call to the first fixed-line telephone number if an active call forwarding condition is not detected.

Brief Description of the Drawings Exemplary embodiments of the invention will be described with reference to the following Figures, in which:

Figure 1 is a block diagram of a communications network;

Figure 2 is a signalling diagram illustrating the signalling between exchanges in the communications network for a telephone call that is not diverted;

Figure 3 is a signalling diagram illustrating the signalling between exchanges in the communications network for a telephone call that is diverted to a mobile telephone number;

Figure 4 is a graph illustrating the time period between ACI messages and ACM messages in a telephone call set up for some non-diverted and diverted telephone calls;

Figure 5 is another graph illustrating the time period between ACI messages and ACM messages in a telephone call set up for some non-diverted and diverted telephone calls;

Figure 6 is another graph illustrating the time period between ACI messages and ACM messages in a telephone call set up for some non-diverted and diverted telephone calls; Figure 7 is another graph illustrating the ACI plus ACM period in a telephone call set up for some non-diverted and diverted telephone calls;

Figure 8 is a graph illustrating the distribution of ACM messages over a large number of telephone calls;

Figure 9 is a block diagram of a network interface function (NIF) unit according to an embodiment of the invention;

Figure 10 is a flow chart illustrating a method of detecting a call forwarding condition according to a general embodiment of the invention; Figure 1 1 is a flow chart illustrating a method of detecting a call forwarding condition according to a specific embodiment of the invention;

Figure 12 is a flow chart illustrating a method of detecting a call forwarding condition according to another specific embodiment of the invention;

Figure 13 is a flow chart illustrating a method according to an embodiment of the invention; and Figure 14 is a flow chart illustrating a method of detecting a call forwarding condition according to another embodiment of the invention.

Detailed Description of the Preferred Embodiments

Figure 1 is a block diagram of a communications network in which the invention can be implemented. The communications network may comprise switches and exchanges belonging to one or more different telephone service providers, including fixed-line and mobile telephone service providers.

In Figure 1 , a calling party apparatus 2 is shown. In the following discussion of the invention, this calling party apparatus 2 is the apparatus that initiates a telephone call for the purpose of determining whether there is an active call forwarding condition on a selected telephone number. In preferred embodiments, the calling party 2 is provided in the form of an apparatus that is placed in or connected to a local switch of a communication network that can initiate telephone calls to selected telephone numbers and monitor the signalling that is sent and/or received during the set up of the telephone call.

In these preferred embodiments, a practical implementation of the invention may comprise the calling party apparatus 2 being managed by a service provider (e.g. that provides a service for identifying telephone numbers with an active call forwarding condition), and the service provider/apparatus can be requested by another party (e.g. a financial institution) to determine whether a selected telephone number has an active call forwarding condition, prior to that other party making a call to that telephone number. In that case, it will be appreciated that the calling party apparatus 2 will likely be connected to a different network switch to the telephone of the requesting party, and/or may be a subscriber to a different network operator to the requesting party. In alternative embodiments, an apparatus is provided that is placed in or connected to a local switch of a communication network that is set up to monitor or 'sniff the signalling that is sent and/or received during the set up of a telephone call by a separate (and in some cases conventional) telephone apparatus connected to that local switch. In this embodiment, a practical implementation may be for a financial institution to implement and operate the calling party apparatus 2 themselves.

In either embodiment described above, the calling party apparatus 2 can be in the form of a network interface function (NIF) unit, which is described in more detail below.

The calling party apparatus 2 is connected by a fixed line 3 to an exchange 4 (labelled Exchange A in Figure 1 ) that belongs to the telephone service provider of the calling party. This exchange 4 is also referred to in the following description as the "outgoing exchange".

The exchange 4 is connected to a public switched telephone network (PSTN) 5 by a signalling link 5. In some embodiments on the invention, the exchange 4 communicates over the signalling link 5 with the PSTN 6 according to the Interconnect User Part (IUP) signalling protocol.

The PSTN in use in the UK comprises two main types of switch, switches known as 'System X' switches, which were the switches used in the UK's first national digital exchange system, and other types of switch, referred to as 'non-System X' switches herein. Similar types of switches are in use in the public telephone networks of other countries. Those skilled in the art will be aware of and understand what is meant by a 'System X' switch, but for the purposes of this disclosure, a System X switch is a switch exhibiting the signalling behaviour shown in Figures 2 and 3 (which are discussed in more detail below).

A 'called party' telephone 7 is shown in Figure 1 that is connected to an exchange 8 (labelled Exchange B in Figure 1 ). The exchange 8 is connected to the PSTN 6 by a signalling link 9. In some embodiments on the invention, the exchange 8 communicates over the signalling link 9 with the PSTN 6 according to the Interconnect User Part (IUP) signalling protocol. In the following discussion of the invention, the called party telephone 7 is the telephone apparatus belonging to the called party, i.e. the party to which the telephone call from the calling party apparatus 2 is directed. The called party telephone 7 is a fixed-line telephone and has an associated fixed-line telephone number that is referred to herein as the "first telephone number" or "first fixed-line telephone number". Thus, when the calling party is initiating the call, the calling party dials the first fixed-line telephone number. Exchange B is also referred to herein as an "incoming exchange".

A 'third party' telephone 10 is shown in Figure 1 that is connected to an exchange 1 1 (labelled Exchange C in Figure 1 ). The exchange 1 1 is connected to the PSTN 6 by a signalling link 12. In some embodiments on the invention, the exchange 1 1 communicates over the signalling link 12 with the PSTN 6 according to the Interconnect User Part (IUP) signalling protocol. The third party telephone 10 may be a fixed-line telephone or a mobile telephone.

In the following discussion of the invention, the third party telephone 10 is a telephone that may belong to the called party (i.e. the same person or business that owns the called party telephone 7) or a third party (e.g. a fraudster). The third party telephone 10 has an associated telephone number that is referred to herein as the "second telephone number" (and which is different to the first telephone number). The second telephone number may be a fixed-line telephone number or a telephone number associated with a mobile telephone network subscriber. Exchange C is also referred to herein as an "incoming exchange". As is known, a call forwarding condition (e.g. an Unconditional Call Forwarding condition) can be set up or activated for the first fixed-line telephone number (associated with the called party telephone 7) so that calls to the first telephone number are diverted to another telephone number, for example the second telephone number associated with the third party telephone 10. In practice, this means that when a call is placed by the calling party apparatus 2 to the first telephone number, call signalling is sent between Exchange A and Exchange B, and then Exchange B, in accordance with the call forwarding condition, establishes signalling with Exchange C, the exchange associated with the second telephone number. Each signalling 'leg' (i.e. from Exchange A to Exchange B and from Exchange B to Exchange C) is treated as a separate call, namely a first call from calling party apparatus 2 to called party telephone 7 and a second call from called party telephone 7 to the third party telephone 10. As noted above, the fact that there is an active call forwarding condition on the first telephone number is not notified back to the originator of a call to the first number in legacy switching systems employed in the PSTN 6 and exchanges 4, 8, 1 1 (such as in the UK PSTN that uses 'System X' and 'non-System X' switches). However, the invention provides a way for an active call forwarding condition (particularly an active Unconditional Call Forwarding condition) to be detected by the calling party in these legacy switching systems. It has been found that the approach required to detect whether a call forwarding condition is active may depend on which type of switch is in use in the communication network between the calling party, the called party and the third party, and also or alternatively whether the telephone number of the third party is a fixed or mobile telephone number. The principles behind each approach are discussed in connection with Figures 2-8 below.

Figure 2 is a signalling diagram illustrating the signalling in a system with System X switches when a call forwarding condition is not active for the first telephone number (i.e. a call to the first telephone number associated with the called party telephone 7 will be connected to the called party telephone 7). The called party telephone 7 may be a fixed telephone or a mobile telephone - the signalling shown in Figure 2 is the same in both cases. Thus, Figure 2 shows the signalling between the calling party apparatus 2, Exchange A and Exchange B, when System X switches are present in the network. The signals shown in Figure 2 are in accordance with the IUP signalling protocol. It will be appreciated that the signalling shown in Figure 2 corresponds to the signalling that occurs in conventional networks when no call forwarding condition is active (i.e. the signalling shown is not changed or affected by the presence of the calling party apparatus 2 according to the invention, and in a conventional network the role of the calling party apparatus 2 in the signalling shown in Figure 2 will be taken by a conventional telephone or switch).

At the start of the process, the first telephone number is dialled on the calling party apparatus 2 (or conventional telephone apparatus) which triggers the transmission of an Initial and Final Address Message (IFAM) message 50 to Exchange A. The IFAM message initiates the set-up of a call between the calling party apparatus 2 and the destination telephone (the called party telephone 7) and contains, amongst other information, the telephone number that has been dialled (i.e. the first telephone number in this case).

The IFAM message 50 is received at Exchange A and forwarded as IFAM message 52 to the exchange (Exchange B) associated with the telephone number contained in the IFAM message 50.

After the IFAM message 52 is received at Exchange B, pairs of Additional Call Information (ACI) messages are exchanged between the calling party apparatus 2 (or conventional telephone apparatus) and Exchange B so that Exchange B can obtain all of the information required to set up the call. ACI messages can be used to request information from the destination node (in which case an information requested, 'IRC, field can indicate the particular information that is requested) or to send information to the source node (in which case an information contained, 'ICC, field can indicate the requested information).

In particular, Exchange B sends a first ACI message 54 requesting the calling party apparatus 2 (or conventional telephone apparatus) provide a full calling line identity (CLI). This request message 54 is received at Exchange A and sent to the calling party apparatus 2 (or conventional telephone apparatus) as ACI message 56.

On receipt of ACI request message 56, the calling party apparatus 2 (or conventional telephone apparatus) transmits an ACI response message 58 that contains the full CLI of the calling party. This message 58 is received by Exchange A and forwarded to Exchange B (as message 60).

Exchange B then requests the calling party apparatus 2 (or conventional telephone apparatus) transmit a presentation number line identity (PNLI) by transmitting another ACI request message 62 to Exchange A. Exchange A forwards this ACI message 62 to the calling party apparatus 2 (or conventional telephone apparatus) as ACI message 64.

On receipt of ACI request message 64, the calling party apparatus 2 (or conventional telephone apparatus) transmits an ACI response message 66 that contains the PNLI of the calling party. This message 66 is received by Exchange A and forwarded to Exchange B as message 68. On receipt of ACI response message 68, Exchange B sends an Address Complete Message (ACM) 70 to Exchange A to indicate that it now has sufficient information to proceed with the call, together with other call progress information. This ACM is received by Exchange A and forwarded to the calling party apparatus 2 (or conventional telephone apparatus) as ACM 72.

If the called party answers their telephone 7 when it rings, an answer message (ANS) 74 is sent by Exchange B to Exchange A, which then forwards the ANS to the calling party apparatus 2 (or conventional telephone apparatus) as ANS 76.

Figure 3 is a signalling diagram illustrating the signalling in a system with System X switches when a call forwarding condition to a second telephone number is active for the first telephone number (i.e. a call to the first telephone number associated with the called party telephone 7 will be diverted to the third party telephone 10 associated with the second telephone number). The third party telephone 10 may be a fixed telephone or a mobile telephone - the signalling shown in Figure 3 is the same in both cases. The signalling in this situation is similar to that shown in Figure 2, although in this case, due to the active call forwarding condition, Exchange B (associated with the first telephone number) forwards signals and messages from the calling party apparatus 2 and Exchange A to the exchange of the third party telephone 10 to which the call is to be diverted (i.e. Exchange C), and vice versa. As with Figure 2 above, it will be appreciated that the signalling shown in Figure 3 corresponds to the signalling that occurs in conventional networks when a call forwarding condition is active (i.e. the signalling shown is not changed or affected by the presence of the calling party apparatus 2 according to the invention, and in a conventional network the role of the calling party apparatus 2 in the signalling shown in Figure 3 will be taken by a conventional telephone or switch). Thus, when the calling party dials the first telephone number an IFAM 80 is generated and sent to Exchange A. Exchange A forwards this IFAM to Exchange B (IFAM 82) and Exchange B forwards the IFAM to Exchange C (IFAM 84). As with the signalling in Figure 2, the IFAM initiates the set-up of a call between the calling party apparatus 2 (or conventional telephone apparatus) and the destination telephone (the third party telephone 10 in this case, although the calling party is not aware of this) and contains, amongst other information, the telephone number that has been dialled (i.e. the first telephone number).

After the IFAM message 84 is received at Exchange C, a pair of Additional Call Information (ACI) messages are exchanged between the calling party apparatus 2 (or conventional telephone apparatus) and Exchange C so that Exchange C can obtain all of the information required to set up the call. Thus, Exchange C sends a first ACI message 86 requesting the full calling line identity (CLI) of the calling party to Exchange B. Exchange B forwards this ACI message to Exchange A (message 88) and Exchange A forwards the ACI message to the calling party apparatus 2 (or conventional telephone apparatus) (signal 90).

The calling party apparatus 2 (or conventional telephone apparatus) responds with the requested information in another ACI message 92 and this passes through Exchanges A and B to arrive at Exchange C (signals 94, 96).

Now, in contrast to the inactive call forwarding situation shown in Figure 2 where a request for the presentation CLI would now be sent from the destination exchange to the originator of the telephone call, in the active call forwarding situation, Exchange C sends an Address Complete Message (ACM) to the calling party apparatus 2 (or conventional telephone apparatus) (signals 98, 100, 102) after receipt of the ACI message 96 containing the full CLI.

Following the transmission of this ACM 98, Exchange C then sends an ACI message 104 requesting the presentation CLI from the calling party. This message 104 is sent to Exchange B, which then forwards the message to Exchange A (signal 106) and on to the calling party apparatus 2 (or conventional telephone apparatus) (signal 108).

The calling party apparatus 2 (or conventional telephone apparatus) responds with an ACI message 1 10 that indicates the presentation CLI and this is sent to Exchange C via Exchanges A and B (signals 1 12 and 1 14).

If the third party answers their telephone 10 when it rings, an answer (ANS) message 1 16 is sent by Exchange C to Exchange B, which then forwards the ANS message to Exchange A (signal 1 18) and on to the calling party apparatus 2 (or conventional telephone apparatus) as ANS message 120. Thus, it can be seen from a comparison of Figures 2 and 3 that, from the point of view of the calling party apparatus 2 (or conventional telephone apparatus), when System X switches are used in the network, the message sequence used in the set up of the telephone call differs depending on whether there is an active call forwarding condition on the called telephone number or not.

In particular, in the situation where there is no active call forwarding condition on the first telephone number, both ACI request messages from the incoming exchange (Exchange B in the example of Figure 2) are received by the calling party apparatus 2 (or conventional telephone apparatus) before an ACM is received. However, in the situation where there is an active call forwarding condition on the first telephone number to a second telephone number belonging to a third party telephone 10, the ACI request for the full CLI is received prior to receiving the ACM (as in Figure 2), but the ACI request for the presentation CLI is received after the ACM.

Thus, in some embodiments of the invention, the order or sequence in which messages are received at the calling party telephone side of the connection can be monitored to make a determination as to whether there is an active call forwarding condition on the first telephone number.

As noted above, there are differences in the sequence in which messages occur in the set up of a call to a first telephone number depending on whether call forwarding is active or not. However, this difference is only found when System-X switches are present/used between the calling party apparatus 2, the called party telephone 7 and the third party telephone 10, and a different approach may be required in order to determine whether there is an active call forwarding condition on the telephone number of the called party telephone 7 if System-X switches are not present/used. The graphs in Figure 4-7 illustrate the results of various test calls for a number of different scenarios in which the timing of the ACI message and ACM message was observed. Each test call was placed from an unspecified network to a number in a fixed line or mobile network, with diverts to fixed or mobile numbers known to be set up in some cases. The legends on each graph indicate the type of call scenario, and the y-axis represents a different test case. In the legends, F1 , F2 and F3 represent three different fixed line network operators and M1 to M5 represent the networks of five different mobile operators. So, for example, the legend "F1 - No divert" in Figure 4 represents a call placed from an unspecified network to a number in fixed line network F1 , and no divert was set up on the number, whereas the legend "F1 - Divert to M3" in Figure 4 represents a call placed from an unspecified network to a number in fixed line network F1 , and a divert was in place to a number in mobile network M3. In each of the graphs, some bracketing has been used to show the general groupings of the test scenarios.

In Figure 4 it can be seen that there is a clear difference in the ACI to ACM period between calls to a fixed line number that were not diverted and those that were diverted to a mobile telephone. The reason for this difference is thought to be due to the time taken by the mobile network to page the mobile phone after the call has been forwarded by the fixed line network. Figure 5 shows results for similar scenarios to those in Figure 4, although in this case, where there is a divert in place to a mobile network, the destination device is in an unusual state, such as being unattached to the mobile network, or the device is a data dongle. As in Figure 4, there is a marked difference in the ACI to ACM period between calls to a fixed line number that were not diverted and those that were diverted to a mobile network.

Figure 6 shows results for a number of test calls to fixed line numbers that are diverted to other fixed line numbers that are different distances from the intended destination for the call. It can be seen that the timings for calls diverted to local fixed line numbers are close to those obtained during the non-diverted calls, with a larger time difference for those a further distance away.

Figure 7 is another graph illustrating a combination of ACI and ACM timings in a telephone call set up for some non-diverted and diverted telephone calls. It was observed that for diverts from a fixed line number to another fixed line number, the initial ACI was delayed, but the ACM remained small.

Figure 8 shows the distribution of the time period between the ACI and ACM for 10000 test telephone calls. Typically it is expected that only around 0.1 % of telephone calls are diverted to another telephone number. Thus Figure 8 shows the distribution of ACI to ACM timings for normal network conditions (i.e. non-diverted), and it can be seen that the standard distribution of these timings is relatively tight, particularly for calls involving System-X switches (which is from around 220ms to around 500ms with a standard deviation around a mean of about 320ms), although there is also a relatively tight distribution for other types of switches from around 580ms to around 1240ms with a standard deviation around a mean of about 700ms. Although not visible in Figure 8 due to the low rates of occurrence of these calls, some calls take a much longer time than average to set up (e.g. up to 6880ms). Thus, given a measured latency (i.e. time period between the AC I and ACM messages) for a particular call, the distribution can be used to determine the probability that the latency is due to an active call forwarding condition.

Thus, in some embodiments of the invention, the timing of messages in the set up of the telephone call (e.g. the time of receipt of messages at the calling party apparatus side of the connection and/or the time of transmission of messages by the calling party apparatus 2) can be monitored to make a determination as to whether there is an active call forwarding condition on the first telephone number. It will be noted from the above graphs that the timing of messages in the set up of the telephone call only generally be used to provide a reliable indication that there is an active call forwarding condition on the first telephone number if the telephone number to which a call is diverted is a mobile telephone number, since the latency is introduced into the message timings in that scenario due to the need for the mobile network to page the mobile telephone. This latency (or at least the level of latency shown in the above Figures) is not present when the first telephone number is diverted to a fixed (landline) telephone number. It will be appreciated however that the timing of messages can be used to detect an active call forwarding condition regardless of the type of switches present or used in the network.

Based on the distribution shown in Figure 8, it can be assumed that a telephone number is likely to have an active call forwarding condition to a mobile telephone number if the time period between the first ACI and the ACM is greater than a certain threshold time period, e.g. 1500ms, and this value can be used as a threshold to determine whether there is an active call forwarding condition. However, it will be appreciated that other values can be selected for the threshold, depending on the sensitivity required for the call forwarding detection (e.g. a lower value can be used but this may increase the number of false positives, i.e. incorrect classifications of an active call forwarding condition, but a higher value may result in more false negatives, i.e. incorrect classifications of an inactive call forwarding condition). Thus, in some embodiments the threshold is 1500ms, but in some embodiments, the threshold used to determine the call forwarding condition can be a higher or lower value. For example the threshold used to determine the call forwarding condition can be a value that is selected from a specified range. A lower limit for the specified range can be 1000ms, 1250ms, or 1500ms. An upper limit for the specified range can be 2000ms, 1750ms or 1500ms.

Figure 9 is a block diagram of an apparatus that can be placed in a communication network and used in some embodiments of the invention to initiate a telephone call to a selected telephone number to determine whether that telephone number has an active call forwarding condition. In other embodiments, an apparatus similar to that shown in Figure 9 can be used to monitor the messages transmitted in the set up of a telephone call to a selected telephone number by another telephone or automated call initiating device.

As noted above, the apparatus 150, which is known in some embodiments as a network interface function (NIF) unit 150, can be placed in or connected to a local switch or telephone of the party implementing the invention. The NIF unit 150 comprises a processing unit 152 that performs the processing required to determine whether there is an active call forwarding condition on a called telephone number. The processing unit 152 is connected to a memory module 154 that can store computer program instructions for execution by the processing unit 152 (for example instructions that allow the processing unit 152 to implement the method according to the invention) and other data, information or computer program instructions necessary for correct operation of the NIF unit 150 and/or for implementing the invention. The NIF unit 150 also comprises a signalling interface 156 that is connected to the processing unit 152 and that allows the processing unit 152 to send and receive signals required to set up telephone calls (and in some embodiments to initiate the telephone call itself). In some embodiments the signalling interface 156 can allow the NIF unit 150 to send an indication to another telephone or computer (for example owned or managed by a financial institution), or other component of the network indicating whether call forwarding is active for the dialled number. In other embodiments (not shown in Figure 9), the NIF unit 150 comprises further communication functionality (for example the ability to connect wirelessly or through a wired connection to the Internet or other type of network) that allows an indication of the call forwarding condition to be provided to the other telephone or computer.

In embodiments where the signalling used in the set up of the telephone calls is in accordance with the IUP protocol, the signalling interface 156 and processing unit 152 are configured to receive and/or monitor IUP signals.

In embodiments where the apparatus 150 is used to monitor the messages in the set up of a telephone call initiated by another telephone apparatus or automated call initiating device, the apparatus 150 can be located near to or be part of that other telephone apparatus or automated call initiating device, or (as shown in Figure 1 ) it can be located near to or be part of a switch that is local to the other telephone apparatus or automated call initiating device and that lies in the signalling path between the other telephone apparatus or automated call initiating device and the local exchange (e.g. Exchange A in Figure 1 ). In either case, the apparatus 150 is able to monitor the signals that are sent and received during the set up of a telephone call to a first telephone number.

In some embodiments, rather than providing a dedicated apparatus 150 for implementing the invention, the functionality of the NIF unit 150 can be provided through software or firmware modifications to one or more existing communication network components (for example a telephone, a switch (not shown in Figure 1 ), or in an exchange associated with the calling party). The flow chart in Figure 10 illustrates a general method of determining whether there is an active call forwarding condition on a first telephone number according to the invention. The method is generally performed by the NIF 150 according to the invention. Firstly, a telephone call is initiated to the first telephone number of a called party (or to any other telephone number for which the call forwarding condition is to be determined). As described above, in some embodiments the telephone call is initiated by the NIF 150 itself, and in other embodiments the telephone call is initiated by another telephone apparatus with the NIF 150 monitoring the messages transmitted and/or received by that apparatus. The telephone call is initiated in a conventional manner, for example by manually dialling the first telephone number on a telephone, or by NIF 150 autonomously dialling the first telephone number, and, in a network that uses the IUP signalling protocol, this results in the transmission of an Initial and Final Address Message (IFAM) to Exchange A.

The set up of the telephone call then proceeds according to the normal procedure, so for example an ACI request is sent to the originator of the telephone call (e.g. the NIF 150 or other telephone apparatus as appropriate) by the exchange of the called party telephone 7 or third party telephone 10 as appropriate depending on whether call forwarding is active or not. In a first step, step 201 , while the telephone call to the first telephone number is being set up, the signals sent and/or received by the originator of the telephone call (e.g. NIF 150 or other telephone apparatus) are monitored.

Depending on the way in which an active call forwarding condition is to be detected, the sequence in which signals occur during the call set up process can be monitored, and/or the timing or time or receipt/transmission of the signals that occur during the call set up process can be monitored. The sequence in which signals occur and/or the timing or time of receipt/transmission of those signals can be stored in the memory module 154 for subsequent analysis by the processing unit 152.

In some embodiments, for example where the NIF 150 is monitoring the messages in a call set up by another telephone or call initiating apparatus, step 201 can comprise monitoring only the incoming signals - i.e. the signals being sent to the originator of the telephone call, and in other embodiments, step 201 can comprise monitoring only the outgoing signals - i.e. the signals being sent by the originator of the telephone call. In yet further embodiments, step 201 can comprise monitoring both the incoming and outgoing signals.

Step 201 can also or alternatively comprise monitoring the signalling only for specific signals that occur during the set up of the telephone call to the first telephone number, and the specific signals can depend on the way in which the call forwarding condition is to be detected. For example, where the call forwarding condition is to be detected from the sequence of signals, it is possible for only the ACI request for the presentation CLI (or the ACI response with the presentation CLI) and the transmission of the ACM to be monitored. Where the call forwarding condition is to be detected from the timing of the signals in the call set up procedure (e.g. the time of receipt/transmission), it is possible for only the timing of the first ACI request/response message and ACM to be monitored.

Next, in step 203, the monitored signals are analysed by apparatus 150 to determine whether there is an active call forwarding condition on the dialled telephone number (the first telephone number in this case). In particular, the call forwarding condition can be determined by analysing the timing and/or sequence of the received/transmitted signals. Where the sequence of signals is analysed, the call forwarding condition can be detected based on a comparison between the monitored sequence of signals and a known signal sequence for a non-diverted telephone call (to any telephone number) and/or a known signal sequence for a diverted telephone call (to any telephone number).

Where the timing of signals is analysed, the call forwarding condition can be detected based on a comparison of an elapsed time between two or more specific signals to a threshold value or range of acceptable values. As noted above, the threshold value can be set to a predetermined value or determined for the communication network based on an analysis of the behaviour of the communication network in various diverted and non-diverted test scenarios.

Specific embodiments of the analysis performed in step 203 are discussed in more detail below with reference to Figures 1 1 and 12.

As noted above, in some embodiments the telephone call to the first telephone number is established merely to determine the call forwarding condition of the first telephone number prior to an actual telephone call being placed to the first telephone number (e.g. by another party such as a financial institution). In this case, the telephone call initiated prior to step 201 is terminated by the calling party apparatus 2 (e.g. by an operator of the NIF 150 or autonomously by the apparatus 150) before the call is answered by the recipient (i.e. the called party or third party as appropriate). In some embodiments the call can be terminated as soon as a specific message has occurred in the call set up procedure. For example the call can be terminated as soon as an ACI request for the presentation CLI is received (in the sequence embodiment) or as soon as an ACM is received (in either the sequence or timing embodiment). Where the initiated telephone call is a test call merely to determine the call forwarding condition, the analysis in step 203 may be performed before or after the call is terminated, as desired.

In other embodiments, the analysis of the call forwarding condition can be performed while the call set up procedure is occurring and an indication provided to the calling party as soon as it is available so that the calling party can decide whether to continue with the call.

Figure 1 1 illustrates a method of determining the call forwarding condition of a first telephone number according to the sequence monitoring embodiment of the invention that can be used in a network that uses IUP signalling. As noted above, this method can be effective in identifying an active call forwarding condition where the signalling network includes System X switches. As in the method of Figure 10, a telephone call is initiated to the first telephone number. The initiation of this call is the same as described above for Figure 10.

While the telephone call to the first telephone number is being set up, the signals sent and received by the originator of the telephone call are monitored (step 301 ). This step is similar to step 201 described above. In this embodiment, at least the occurrence of the ACI requests or responses and the Address Complete Message (ACM) are monitored, and preferably the occurrence of at least the ACI request for the presentation CLI or ACI reply with that information is monitored.

Then, in step 303, the call forwarding condition is identified by examining the monitored signals and determining whether an ACI request was received or sent after the ACM.

If the ACI request (in particular for the presentation CLI) was received or sent after the ACM was received or sent (e.g. corresponding to the signalling sequence shown in Figure 3), then it is determined that there is an active call forwarding condition on the first telephone number (step 305).

If the ACI request (in particular for the presentation CLI) was received or sent before the ACM was received or sent (e.g. corresponding to the signalling sequence shown in Figure 2), then it is determined that there is no active call forwarding condition on the first telephone number (step 307).

In either case (step 305 or 307), an indication of the call forwarding condition (i.e. active or inactive) can be provided to another party (e.g. a financial institution or other party interested in the call forwarding condition on the first telephone number).

Figure 12 illustrates a method of determining the call forwarding condition of a first telephone number according to the timing monitoring embodiment of the invention that can be used in a network that uses IUP signalling. As noted above, this method can be effective in identifying an active call forwarding condition to a mobile telephone number regardless of the types of switches used in the signalling network. As in the method of Figure 10, a telephone call is initiated to the first telephone number. The initiation of this call is the same as described above for Figure 10 and Figure 1 1 .

While the telephone call to the first telephone number is being set up, the signals sent and received by the originator of the telephone call are monitored (step 401 ). This step is similar to step 201 described above. In this embodiment, the timing (e.g. time of receipt at the apparatus 150) of the ACI requests or responses and the Address Complete Message (ACM) can be monitored. The timing can be recorded as absolute time or a time relative to some event, for example the transmission of the IFAM at the start of the call procedure. Alternatively, this step can comprise starting a timer on receipt or transmission of the first ACI request/response in the call set up procedure, and monitoring the time elapsed until receipt of the ACM.

Then, in step 403, the call forwarding condition is identified by examining the monitored signals and determining whether time elapsed between the first ACI message and receipt of the ACM exceeds a threshold. As noted above in connection with Figure 8, the threshold for the time period between the first ACI message and the ACM can be set at, or around, 1500ms. However, alternative values for the threshold can be chosen depending on the specific characteristics of the communication network.

If the time between the first ACI message and the ACM is greater than the threshold, then it is determined that there is an active call forwarding condition on the first telephone number (step 405). If the time between the first ACI message and the ACM is less than the threshold the ACI request, then it is determined that there is no active call forwarding condition on the first telephone number (step 407). In either case (step 405 or 407), an indication of the call forwarding condition (i.e. active or inactive) can be provided to another party (e.g. a financial institution or other party interested in the call forwarding condition on the first telephone number).

Figure 13 illustrates a method that can be performed when the invention is implemented into a communication network in order to determine which technique should be used to determine the call forwarding condition. In a first step, step 501 , the architecture of the communication network that hosts the first telephone number is determined. In particular embodiments, step 501 comprises determining the type of switches used in the network.

If the switches in the communication network are System X switches (step 503), then it is determined that the sequence of signals should be monitored to determine the call forwarding condition (step 505). Otherwise, the timing of signals can be monitored to determine the call forwarding condition (step 507).

If it is not possible to determine whether the network uses System X switches, steps 501 and 503 can be replaced by a step of performing a number of test calls to telephone numbers whose call forwarding condition is known and a step of analysing the test calls to determine the behaviour of the network and thus which technique is most appropriate for determining the call forwarding condition.

As an alternative to Figure 13, as illustrated in Figure 14, if the architecture of the communication network is not known in advance of the call to the first telephone number being initiated (for example if the tests described above for Figure 13 are inconclusive or if no attempt has been made to determine the network architecture), then both the signal sequence and signal timings may be monitored to determine whether there is an active call forwarding condition.

In particular, in step 601 of Figure 14, following the initiation of a telephone call to a first telephone number (which is initiated in a similar way to the call in the methods of Figures 10-12 described above), the sequence and timing of signals used in the set up of the telephone call to the first telephone number is monitored. In this embodiment, at least the occurrence of the ACI requests or responses and the Address Complete Message (ACM) are monitored, and preferably the occurrence of at least the ACI request for the presentation CLI or ACI reply with that information is monitored.

Then, in step 603, it is determined if there is an active call forwarding condition by examining the monitored signals and determining whether an ACI request was received or sent after the ACM. If the ACI request (in particular for the presentation CLI) was received or sent after the ACM was received or sent (e.g. corresponding to the signalling sequence shown in Figure 3), then it is determined that there is an active call forwarding condition on the first telephone number (step 605). If the ACI request (in particular for the presentation CLI) was received or sent before the ACM was received or sent (e.g. corresponding to the signalling sequence shown in Figure 2), then the method proceeds to step 607 in which it is determined if there is an active call forwarding condition by examining the monitored signals and determining whether time elapsed between the first ACI message and receipt of the ACM exceeds a threshold. As noted above in connection with Figure 8, the threshold for the time period between the first ACI message and the ACM can be set at, or around, 1500ms. However, alternative values for the threshold can be chosen depending on the specific characteristics of the communication network. If the time between the first ACI message and the ACM is greater than the threshold, then it is determined that there is an active call forwarding condition on the first telephone number (step 605).

If the time between the first ACI message and the ACM is less than the threshold the ACI request, then it is determined that there is no active call forwarding condition on the first telephone number (step 609), since the analysis of the message sequence also did not indicate an active call forwarding condition.

In either case (step 605 or 609), an indication of the call forwarding condition (i.e. active or inactive) can be provided to another party (e.g. a financial institution or other party interested in the call forwarding condition on the first telephone number). There is therefore provided a method and apparatus for detecting whether a fixed- line/landline telephone number has an active call forwarding condition. It will be appreciated that the detailed embodiments of the invention described and illustrated above are exemplary and the invention is not limited to the described embodiments. Instead, the scope of the invention is only to be limited by the claims. In particular, those skilled in the art will appreciate from a study of the drawings, the description and the claims that variations to the disclosed embodiments can be effected in practicing the claimed invention. The word "comprising" as used in the claims does not exclude the presence of other features or steps. Likewise, the indefinite article "a" or "an" in respect of a feature or function does not exclude the possibility of the invention comprising a plurality of said features or functions. Although certain features may be recited in different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. Where reference signs are used in the claims, this should not be construed as limiting their scope.

The processing unit may comprise any type of processor or processor architecture that is suitable for implementing the functions and steps described above, and may comprise single-core or multi-core processors. Where the invention is implemented as a computer program or firmware, the computer program or firmware may be stored or distributed on any suitable medium, such as an optical disc or a solid-state memory module supplied together with or as part of other hardware. Alternatively it may be distributed in other ways, such as via the Internet or through wired or wireless communication systems.