CA2171076A1 - Method for preventing fraud in an inband signalling telephony system and trunk module realizing such a method - Google Patents
Method for preventing fraud in an inband signalling telephony system and trunk module realizing such a methodInfo
- Publication number
- CA2171076A1 CA2171076A1 CA 2171076 CA2171076A CA2171076A1 CA 2171076 A1 CA2171076 A1 CA 2171076A1 CA 2171076 CA2171076 CA 2171076 CA 2171076 A CA2171076 A CA 2171076A CA 2171076 A1 CA2171076 A1 CA 2171076A1
- Authority
- CA
- Canada
- Prior art keywords
- inband
- signal
- trunk module
- signal path
- terminal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- Data Exchanges In Wide-Area Networks (AREA)
Abstract
The disclosed method prevents fraud in an inband signalling telephony system, such as a No. 5 signalling system. It includes a first step of detecting a fraudulent inband signal at a predetermined location of an outgoing signal path between an input terminal Os and an output terminal Oss of a trunk module T included in the inband signalling telephony system. The predetermined location is situated between the input terminal Os and an injection terminal I of the outgoing signal path where an inband signal can be injected. In a second step, the fraudulent inband signal is removed from the outgoing signal path by interrupting this path during a time interval at least equal to the duration of the inband signal.
The trunk module realizing this method includes a receiver similar to the receivers used in the inband signalling path of the trunk module to detect incomming inband signals and to filter these out before transmitting the signal to a user station connected to the trunk module.
This receiver is coupled betwwen the above mentioned input terminal Os and the injection terminal I.
The trunk module realizing this method includes a receiver similar to the receivers used in the inband signalling path of the trunk module to detect incomming inband signals and to filter these out before transmitting the signal to a user station connected to the trunk module.
This receiver is coupled betwwen the above mentioned input terminal Os and the injection terminal I.
Description
_ METHOD FOR PREVENTING FRAUD IN AN INBAND SIGNALLING
TELEPHONY SYSTEM AND TRUNK MODULE REALIZING SUCH A METHOD
The present invention relates to a method for preventing fraud in an inband signalling telephony system.
The problem of fraud with respect to inband signalling telephony systems, e.g. No. 5 signalling systems, is well known and especially applies to international systems and to "free-phone", i.e.
international toll-free phone. So called "hackers" can via a normal phone inject inband signals in an outbound signalling path of a telephony system in such a way that they get access to this telephony system. A detailed description of the fraud problem in No. 5 signalling systems can be found in the paper distributed at the International Network Abuse Prevention meeting held in Brussels on 6-7 May 1992 "CCITT No. 5 Bluebox Fraud" by A.S. Foote of AT&T. The problem is also acknowledged in the CCITT Temporary Document XI/1-16 of Working Party XI/1, Geneva 10 - 12 March 1992, Question 7/XI p. 3, item 10.
In the CCITT Recommendations Q.141 Fascicle VI.2, chapter II, p. 58, item h) measures are proposed to detect such fraud attempt and to possibly react thereon. However, these measures rely on actions to be taken by both sides of a communication. As such a communication can be an international one this implies an agreement to be followed by different national operators or administrations which is often difficult to realize.
Therefore, the object of the present invention is to provide a method for preventing fraud in the above type of telephony networks, but which does not rely on the goodwill of operators or administrations.
This object is realized due to the fact that said method includes the steps of :
- detecting a fraudulent inband signal at a predetermined location of an outgoing signal path between an input terminal and an output terminal of a trunk module 2 1 ~ t O76 included in said inband signalling telephony system, said predetermined location being situated between said input terminal and an injection terminal of said outgoing signal path where an inband signal can be injected; and - removing a said fraudulent inband signal from said outgoing signal path when detected.
When in the first mentioned step an inband signal is detected, this means that someone has in a fraudulous way injected this signal, since normally, this signal should only appear after the injection terminal. This signal is then removed from the outgoing signal path.
An additional feature of the present invention is that said step of removing said fraudulent inband signal is realized by interrupting said outgoing signal path between said input terminal and said injection terminal, for a predetermined time interval. This time interval has to be such that the fraudulent inband signal is intercepted without losing speech signals, i.e. it has at least to be equal to the duration of the fraudulent signal, but it may not overlap the time interval used for the transmission of speech signals.
A second object of the invention is to provide a trunk module realizing the above method.
This is achieved by means of a trunk module including an input terminal and an output terminal between which an outgoing signal path can be established, and an inband signal generation means having an output coupled to an injectior terminal of said outgoing signal path and adapted to g~nerate inband signals, said trunk module additionally lncluding an inband signal detection means coupled to said outgoing signal path between said input terminal and said injection terminal and adapted to detect inband signals and a removal means coupled between said input terminal and said injection terminal and adapted to remove a said inband signal from said outgoing signal path 2 t ~ I 0 76 _ under control of an output signal of said inband detection means, when detected.
An additional characteristic feature of this trunk module is that said removal means includes interruption means to interrupt said outgoing si?nal path during a predetermined time interval. As mentioned earlier this predetermined time interval has to be such that the inband signal intercepted without losing speech signals.
Yet another characteristic feature of the trunk module according to the invention is that said trunk module additionally includes a second inband signal detection means and a second removal means similar to the first mentioned signal detection means and the first mentioned removal means to detect and remove inband signals on and from an incoming signal path of said trunk module respectively.
It is well known that trunk modules of inband signalling telephony systems include inband signal detection circuitry and removal circuitry to detect and extract inband signals on and from incomming signalling paths. This circuitry is included in well known receivers of the trunk module. Similar circuitry can be used to detect the fraudulent inband signals in the outgoing signal path and remove it from that path. As a result, no additional development effort is required to realize the first mentioned detection circuitry and removal circuitry thereby realizing a very efficient design of the subject trunk module.
The above mentioned and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of an embodiment taken in conjunction with the accompanying drawing which schematiccally represents a trunk module T according to the invention.
21~0~6 _ The trunk module T is a No. 5 signalling trunk module included in a No. 5 signalling telephony system (not shown). It includes a receiver module REC1 coupled between an input terminal Iss and an output terminal Is. An input terminal Os is connected to an input of another receiver module REC2, similar to REC1, and an output of REC2 is connected to an input of a sender module SEN, an output of which is coupled to an output terminal Oss of T.
The trunk module T is able to receive at its input terminal Iss a likenamed input signal consisting of a speech signal and an inband signal. The inband signal is in the receiver module REC1 filtered out and only the speech signal Is is provided at the output terminal IS to be transmitted to a subscriber station (not shown).
A signal Os applied at the terminal Os by a subscriber station is applied to REC2 in order to detect and filter out possible inband signals. A resultant signal is applied to SEN which adds a No. 5 signal thereby obtaining the outgoing signal Oss. The location at which the No. 5 signal is added is in the figure represented by an injection terminal I located in the circuitry of SEN.
Normally the signal Os should only contain speech signals since the No. 5 signalling is added to the signal provided by the subscriber station by SEN. Detection in REC2 of an inband signal thus means that someone is trying to get access to the system in a fraudulous way. This signal is then filtered out by REC2.
SEN and, REC1 and REC2, are a sender ind receivers realized according to the CCITT Recommendations Q143 and Q144 respectively. Their realization according to the latter standard being obvious for a person skilled in the art, they are not described in further details.
While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made - 2~ 71 0,76~
only by way of example and not as a limitation on the scope of the invention.
TELEPHONY SYSTEM AND TRUNK MODULE REALIZING SUCH A METHOD
The present invention relates to a method for preventing fraud in an inband signalling telephony system.
The problem of fraud with respect to inband signalling telephony systems, e.g. No. 5 signalling systems, is well known and especially applies to international systems and to "free-phone", i.e.
international toll-free phone. So called "hackers" can via a normal phone inject inband signals in an outbound signalling path of a telephony system in such a way that they get access to this telephony system. A detailed description of the fraud problem in No. 5 signalling systems can be found in the paper distributed at the International Network Abuse Prevention meeting held in Brussels on 6-7 May 1992 "CCITT No. 5 Bluebox Fraud" by A.S. Foote of AT&T. The problem is also acknowledged in the CCITT Temporary Document XI/1-16 of Working Party XI/1, Geneva 10 - 12 March 1992, Question 7/XI p. 3, item 10.
In the CCITT Recommendations Q.141 Fascicle VI.2, chapter II, p. 58, item h) measures are proposed to detect such fraud attempt and to possibly react thereon. However, these measures rely on actions to be taken by both sides of a communication. As such a communication can be an international one this implies an agreement to be followed by different national operators or administrations which is often difficult to realize.
Therefore, the object of the present invention is to provide a method for preventing fraud in the above type of telephony networks, but which does not rely on the goodwill of operators or administrations.
This object is realized due to the fact that said method includes the steps of :
- detecting a fraudulent inband signal at a predetermined location of an outgoing signal path between an input terminal and an output terminal of a trunk module 2 1 ~ t O76 included in said inband signalling telephony system, said predetermined location being situated between said input terminal and an injection terminal of said outgoing signal path where an inband signal can be injected; and - removing a said fraudulent inband signal from said outgoing signal path when detected.
When in the first mentioned step an inband signal is detected, this means that someone has in a fraudulous way injected this signal, since normally, this signal should only appear after the injection terminal. This signal is then removed from the outgoing signal path.
An additional feature of the present invention is that said step of removing said fraudulent inband signal is realized by interrupting said outgoing signal path between said input terminal and said injection terminal, for a predetermined time interval. This time interval has to be such that the fraudulent inband signal is intercepted without losing speech signals, i.e. it has at least to be equal to the duration of the fraudulent signal, but it may not overlap the time interval used for the transmission of speech signals.
A second object of the invention is to provide a trunk module realizing the above method.
This is achieved by means of a trunk module including an input terminal and an output terminal between which an outgoing signal path can be established, and an inband signal generation means having an output coupled to an injectior terminal of said outgoing signal path and adapted to g~nerate inband signals, said trunk module additionally lncluding an inband signal detection means coupled to said outgoing signal path between said input terminal and said injection terminal and adapted to detect inband signals and a removal means coupled between said input terminal and said injection terminal and adapted to remove a said inband signal from said outgoing signal path 2 t ~ I 0 76 _ under control of an output signal of said inband detection means, when detected.
An additional characteristic feature of this trunk module is that said removal means includes interruption means to interrupt said outgoing si?nal path during a predetermined time interval. As mentioned earlier this predetermined time interval has to be such that the inband signal intercepted without losing speech signals.
Yet another characteristic feature of the trunk module according to the invention is that said trunk module additionally includes a second inband signal detection means and a second removal means similar to the first mentioned signal detection means and the first mentioned removal means to detect and remove inband signals on and from an incoming signal path of said trunk module respectively.
It is well known that trunk modules of inband signalling telephony systems include inband signal detection circuitry and removal circuitry to detect and extract inband signals on and from incomming signalling paths. This circuitry is included in well known receivers of the trunk module. Similar circuitry can be used to detect the fraudulent inband signals in the outgoing signal path and remove it from that path. As a result, no additional development effort is required to realize the first mentioned detection circuitry and removal circuitry thereby realizing a very efficient design of the subject trunk module.
The above mentioned and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of an embodiment taken in conjunction with the accompanying drawing which schematiccally represents a trunk module T according to the invention.
21~0~6 _ The trunk module T is a No. 5 signalling trunk module included in a No. 5 signalling telephony system (not shown). It includes a receiver module REC1 coupled between an input terminal Iss and an output terminal Is. An input terminal Os is connected to an input of another receiver module REC2, similar to REC1, and an output of REC2 is connected to an input of a sender module SEN, an output of which is coupled to an output terminal Oss of T.
The trunk module T is able to receive at its input terminal Iss a likenamed input signal consisting of a speech signal and an inband signal. The inband signal is in the receiver module REC1 filtered out and only the speech signal Is is provided at the output terminal IS to be transmitted to a subscriber station (not shown).
A signal Os applied at the terminal Os by a subscriber station is applied to REC2 in order to detect and filter out possible inband signals. A resultant signal is applied to SEN which adds a No. 5 signal thereby obtaining the outgoing signal Oss. The location at which the No. 5 signal is added is in the figure represented by an injection terminal I located in the circuitry of SEN.
Normally the signal Os should only contain speech signals since the No. 5 signalling is added to the signal provided by the subscriber station by SEN. Detection in REC2 of an inband signal thus means that someone is trying to get access to the system in a fraudulous way. This signal is then filtered out by REC2.
SEN and, REC1 and REC2, are a sender ind receivers realized according to the CCITT Recommendations Q143 and Q144 respectively. Their realization according to the latter standard being obvious for a person skilled in the art, they are not described in further details.
While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made - 2~ 71 0,76~
only by way of example and not as a limitation on the scope of the invention.
Claims (7)
1. Method for preventing fraud in an inband signalling telephony system, characterized in that said method includes the steps of :
- detecting a fraudulent inband signal at a predetermined location of an outgoing signal path between an input terminal (Os) and an output terminal (Oss) of a trunk module (T) included in said inband signalling telephony system, said predetermined location being situated between said input terminal (Os) and an injection terminal (I) of said outgoing signal path where an inband signal can be injected; and - removing a said fraudulent inband signal from said outgoing signal path when detected.
- detecting a fraudulent inband signal at a predetermined location of an outgoing signal path between an input terminal (Os) and an output terminal (Oss) of a trunk module (T) included in said inband signalling telephony system, said predetermined location being situated between said input terminal (Os) and an injection terminal (I) of said outgoing signal path where an inband signal can be injected; and - removing a said fraudulent inband signal from said outgoing signal path when detected.
2. Method according to claim 1, characterized in that said step of removing said fraudulent inband signal is realized by interrupting said outgoing signal path between said input terminal (Os) and said injection terminal (I), for a predetermined time interval.
3. Method according to claim 2, characterized in that said predetermined time interval is at least equal to the time duration of said fraudulent inband signal.
4. Trunk module (T) included in an inband signalling telephony system, said trunk module including an input terminal (Os) and an output terminal (Oss) between which an outgoing signal path can be established, and an inband signal generation means (SEN) coupled to an injection terminal of said outgoing signal path and adapted to generate inband signals, characterized in that said trunk module additionally includes an inband signal detection means (REC2) coupled to said outgoing signal path between said input terminal (Os) and said injection terminal (I) and adapted to detect inband signals and a removal means (REC2) coupled between said input terminal and said injection terminal (I) and adapted to remove a said inband signal from said outgoing signal path under control of an output signal of said inband detection means, when detected.
5. Trunk module according to claim 4, characterized in that said removal means includes interruption means to interrupt said outgoing signal path during a predetermined time interval.
6. Trunk module according to claim 4, characterized in that said trunk module additionally includes a second inband signal detection means and a second removal means (REC1) similar to the first mentioned signal detection means and the first mentioned removal means to detect and remove inband signals on and from an incoming signal path of said trunk module respectively.
7. Trunk module according to claim 5, characterized in that said predetermined time interval is at least equal to the duration of said detected inband signal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP95200761.5 | 1995-03-27 | ||
| EP95200761 | 1995-03-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2171076A1 true CA2171076A1 (en) | 1996-09-28 |
Family
ID=8220132
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2171076 Abandoned CA2171076A1 (en) | 1995-03-27 | 1996-03-05 | Method for preventing fraud in an inband signalling telephony system and trunk module realizing such a method |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU4795196A (en) |
| CA (1) | CA2171076A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107872590A (en) * | 2016-09-26 | 2018-04-03 | 北京搜狗科技发展有限公司 | A kind of method, apparatus and equipment of phone identification |
-
1996
- 1996-03-05 CA CA 2171076 patent/CA2171076A1/en not_active Abandoned
- 1996-03-08 AU AU47951/96A patent/AU4795196A/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107872590A (en) * | 2016-09-26 | 2018-04-03 | 北京搜狗科技发展有限公司 | A kind of method, apparatus and equipment of phone identification |
Also Published As
| Publication number | Publication date |
|---|---|
| AU4795196A (en) | 1996-10-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |