FR3068816B1 - DEVICE AND METHOD FOR DETECTING PIRACY OF SURVEILLANCE EQUIPMENT. - Google Patents

Abstract

The invention relates to a device A for preventing an intrusion on a computer network R connected to a device D powered by a data communication cable E, comprising means for measuring a value of the current absorbed by the equipment D and means for interrupting the data communication when the current value becomes less than a threshold value. The invention also relates to an associated method.

Description

The present invention relates to the field of security of surveillance networks. The invention relates in particular to the security of surveillance equipment placed outside a room to be protected. This equipment can be surveillance cameras.

Such surveillance equipment, such as cameras, can be installed outside a room. This equipment is often supplied with energy by a cable used for data transmission. This cable can be an Ethernet cable that simultaneously supplies power to the equipment, known by the acronym PoE, from the English "Power on Ethernet". Such a cable can be physically accessible and be used for intrusion into a computer system that the cable connects to the equipment. Thus, we can cut the cable to connect a pirate device. This pirate device can be provided to lure or penetrate the computer system.

The object of the invention is to propose a protection device and / or method which would make it possible to detect or prevent an intrusion which would use the cable of an external surveillance equipment.

To achieve its object, the invention provides a device for preventing an intrusion on a computer network connected to an equipment supplied with energy by a data communication cable, this device comprising means for measuring a value of the current absorbed by the equipment. in the cable and means for interrupting data communication in the cable when the value of the absorbed current becomes less than a threshold value.

Thus, a device for preventing an intrusion into a system comprising an equipment and a computer network providing a source for the electrical supply of the equipment, can comprise: - a first connector for a first data communication and power cable electric connected to said source; - a second connector for a second cable for data communication and the power supply connected to the equipment; - at least one pair of data communication lines, connecting the connectors together; - for each communication line, a direct link mounted in parallel with the communication line to circulate there a supply current absorbed by the equipment, separately from the data; - cut-off means to interrupt the communication lines between said connectors; - means for measuring a value of the current absorbed by the equipment; and, - control means for comparing the measured value with a threshold value and triggering an opening of the cut-off means when the measured value drops below the threshold value.

The device advantageously comprises a local electrical supply derived from the source, in particular for supplying the control means.

The measured value is preferably an absolute value of the current absorbed by the equipment.

To separate data and power, a device according to the invention can include isolation transformers mounted so that each communication line is isolated between two respective transformers and that the respective direct link connects these two transformers in a non-isolated manner. .

Each cable can be of the Ethernet cable type.

A second object of the invention relates to a method for preventing an intrusion on a computer network connected to an equipment supplied with energy by a data communication cable, characterized in that a value of the current absorbed by the equipment is measured in the cable and in that the data communication in the cable is interrupted when said value of the absorbed current becomes less than a threshold value.

Several embodiments of the invention will be described below, by way of nonlimiting examples, with reference to the accompanying drawings in which: - Figure 1 is a schematic view illustrating the principle of the invention; and, - Figure 2 illustrates an example of implementation of the system of Figure 1.

Figure 1 schematically illustrates the principle of the invention. In the example illustrated, an item of equipment D is supplied with energy by a power source S, using an Ethernet cable E. The electrical power source E is part of a computer network R with which the Equipment D can exchange information. In the example illustrated, the equipment D is a camera placed outside Ext of a Room N. The source S and the network R are inside the room N. In the example illustrated, the network R includes, or is connected to, an alarm system W.

According to the invention, a vigilance device A is arranged in series on the cable E, between the source S and the equipment D. The device being mounted in series on the Ethernet cable E, the latter is, for practical reasons, consisting of a first cable El, which connects the source S to the vigilance device A and a second cable E2 which connects this device to the equipment D. The vigilance device A is designed to monitor the cable E in order to detect an attempt to intrude into the network R and to end this attempt. For this purpose, the vigilance device A monitors the supply current flowing through the cable, intended for the equipment D monitored. Thus, the vigilance device A monitors the current absorbed by the equipment D and supplied by the source S. The vigilance device A is advantageously placed inside the room N, so that it is not directly accessible by someone who tries to intrude on network R.

In this example, the vigilance device A is supplied by the source S, via the Ethernet cable E; the vigilance system is designed to consume as little as possible. The equipment D communicates with the network R via the Ethernet cable E, by means of communication lines L1-L4 each comprising a respective pair of wires P1-P4; a cable generally includes two or four pairs of wires. A supply current supplied by the source S flows through one or more of the pairs of cables. In the example illustrated in detail in FIG. 2, the Ethernet cable E comprises four communication lines L1-L4, therefore four pairs of wires P1-P4.

A first line L1 among the communication lines L1-L4 corresponds to a first pole for a first possible supply circuit and a third line L3 corresponds to a second pole, complementary to the first pole, of this same first circuit L1, L3.

A second line L2 among the communication lines L1-L4 corresponds to a first pole for a second possible supply circuit and the fourth line L4 corresponds to a second pole, complementary to the first pole, of this same second circuit L2, L4.

In the example illustrated in FIG. 2, the first cable El is connected upstream of the vigilance device A by means of a first connector Cl; the second cable E2 is connected downstream of the vigilance device A thanks to a second connector C2. The connectors are here of RJ45 type.

Each connector C1, C2 comprises an isolation transformer Tl, T2 respective for each pair. Thus, inside the vigilance device A, each pair P1-P2 is isolated between two transformers T1, T2 respectively. A continuity of the pairs P1-P4 is ensured so that the data transmission can take place through the transformers. For each pair, a direct link LD, dedicated to the power supply, connects the common mode, upstream of the transformer T1 of the first connector C1, up to the common mode downstream of the transformer T2 of the second connector C2. Thus, the data transmission is separated in the P1-P2 pairs from the power transmission in the corresponding direct link LD.

As illustrated in the figure, between the respective transformers Tl, T2, each line L1-L4 is connected to the downstream coil of the upstream transformer Tl, on the one hand, and, to the upstream coil of the downstream transformer T2, on the other hand . In addition, each direct link LD connects the midpoint of the upstream coil of the upstream transformer T1 and the midpoint of the downstream coil of the downstream transformer T2.

Cut-off means SC are arranged between the connectors C1-C2. These cut-off means SC are designed so as to take an open position in which each wire of each pair P1-P4 is interrupted and a closed position in which the continuity of each wire of each pair is ensured, between the connectors C1, C2. In the example illustrated, the cut-off means SC are designed to substantially interrupt the wires of all the pairs. The breaking means are not designed to interrupt direct links, whether open or closed.

Thanks to this arrangement, the data is transmitted between the connectors C1, C2 only by the pairs PI, P2. Data is not transmitted by LD direct links. For each pair, the power supply is transmitted in parallel by the respective direct link LD. The supply of the equipment D can thus be maintained by the direct links LD, even when the cut-off means SC are open. Thus, it is possible to prevent the transmission of data through the vigilance device A, while maintaining the transmission of the electric power there.

In the example illustrated, the supply of the device D can be provided either by the first supply circuit L1, L3 or by the second supply circuit L2, L4. It is generally not possible to know which of the two circuits actually supplies the equipment D. It is also not possible to know the direction of current flow in this circuit.

In order to ensure that the supply current is effectively measured, a current sensor K1, K2 is mounted in each of the circuits. Thus, in the example illustrated, a first current sensor K1 is mounted on a third direct link L3 and a second current sensor K2 is mounted on a fourth direct link LD4. The third direct link LD3 corresponds, among the direct links LD, to the third communication line L3 and the fourth direct link LD4 corresponds, among the direct links LD, to the fourth communication line L4.

The first sensor Kl measures a first current Jl in the first supply circuit Ll, L3. The second sensor K2 measures a second current J2 in the first supply circuit L2, L4.

The vigilance device A further comprises a microcontroller MC and a local power supply SL for the microcontroller. The local power supply SC is derived from the source S from the lines LD. The derivation is carried out using two diode bridges P, each connected to a supply circuit L1, L3; L2, L4 respectively. Thus, the local supply SL is suitably ensured, whatever the effective supply circuit and the direction of the current in this circuit.

The sensors K3, K4 are connected to the controller MC, so that they transmit to it the values J1, J2 of the measured current. One of the values Jl, J2 is always zero, only one of the circuits L1, L3; L2, L4 actually serving to power the equipment D.

A current threshold value JS has been recorded in the microcontroller MC. The microcontroller MC is provided for comparing the value J1, J2 of the current in the effective circuit with the threshold value JS. Since the direction of the current in the effective supply circuit is not known, the microcontroller MC compares the absolute value | J1 | or | D2 | of the current in the effective circuit with the threshold value JS.

Someone can disconnect the equipment D in order to replace it with a pirate device and in order to attempt an intrusion on the network R. when the equipment is disconnected, the current absorbed by the equipment D and supplied by the source S falls below a JS threshold value.

If the absolute value (Jl |, | J2 | of the current in the effective circuit drops below the threshold value JS, this means that the equipment no longer absorbs current. We can therefore consider that this equipment has been disconnected. disconnection is, as a precaution, considered voluntary, for an intrusive purpose.

Thus, the microcontroller MC is provided to trigger an opening of the cut-off means SC when the absolute value) J11, | J2 | of the current in the effective circuit drops below the JS threshold value. Data transmission is then made impossible between the network R and a pirate device which would be substituted for the equipment D. The intrusion is thus neutralized. The vigilance device A informs the alarm system W of this intrusion attempt.

It is noted that the IEEE 802.3af standard, published on July 11, 2003, defining the PoE type devices provides that the source S verifies that a device is connected to the end of the cable E. Thus, the source S "discovers" l equipment which it must supply by load resistance analysis. The equipment must therefore meet the same standard. As long as an item of equipment is "discovered", the power supplied by the source S is maintained. The power supplied by the source S is cut off at the expiration of a given time, generally a few fractions of seconds, generally close to 10 milliseconds, during which no equipment is discovered.

In the example illustrated, the local supply SL of the vigilance device being derived from the source S, a cut in the general supply supplied by the source S implies a cut in the supply derived by SL.

When an intrusion attempt is made using a pirate device, the removal of equipment D results in an automatic cut-off of the general and local power supply. The connection of the pirate device generates an automatic restoration of the general and local supply. This can have the consequence: - if the vigilance device has not had time to open the cut-off means before cutting the power supply, keeping these means in the closed position; - If the vigilance device has had time to open the cut-off means before cutting off the supply, the return of these means to the closed position.

According to the invention, two solutions are proposed to avoid these consequences.

In a first solution, the vigilance device A comprises phantom charging means. The phantom charging means are designed to simulate the presence of fictitious equipment at the terminals of the source S. Thus, the source S "discovering" an equipment, although fictitious, even when the real equipment D is removed, the general and maintained supply, and the vigilance device remains supplied by the source S.

In a second solution, the vigilance device comprises an intrusion memory. When the current value drops below the threshold value JS, the intrusion memory takes an intrusion value. The memory value is maintained even when the power is turned off. Thus, when the power is restored, the vigilance device A recognizes the value of intrusion and keeps the cut-off means open, or open them if they are not already open.

The vigilance device A also comprises a push button BP, accessible to an operator. The BP button is used to control the microcontroller in order to restore the cut-off means to their closed position, when any risk of intrusion has been eliminated.

Of course, the invention is not limited to the preferred embodiments which have just been described but, on the contrary, the invention is defined by the claims which follow.

It will appear to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching which has just been disclosed to him.

Claims (5)

1. Device (A) to prevent intrusion into a system comprising an equipment (D) and a computer network (R) providing a source (S) for the electrical supply of said equipment (D), characterized in that it comprises : a first connector (Cl) for a first cable (El) for data communication and electrical supply connected to said source (S); -a second connector (C2) for a second cable (E2) for data communication and the power supply connected to said equipment (D); - at least one pair of lines (Lî, L3; L2, L4) of data communication, connecting said connectors (Cl, C2) to each other; -for each communication line (L1-L2), a direct link (LD) mounted in parallel with said communication line to circulate there a supply current (Ji, J2) absorbed by said equipment (D), separately from said data; cut-off means (SC) for interrupting said communication lines (Ll, L3; L2, L4) between said connectors (Cl, C2); - means (K1, K2) for measuring a value (| J1 [, | J2 |) of said current absorbed by said equipment (D); and, control means (MC) for comparing said measured value | J2 |) with a threshold value (JS) and triggering an opening of said breaking means (SC) when said measured value drops below said threshold value 2. Device according to claim 1, characterized in that it comprises a local electrical supply (SL) derived from the source (S) in particular for supplying the control means (MC). 3. Device according to one of claims 1 and 2, characterized in that the measured value is an absolute value (| J1 |, | J2j) of said current absorbed by said equipment (D). 4. Device according to one of claims 1 to 3, characterized in that it comprises isolation transformers (T1, T2) mounted so that each communication line (L1-L4) is isolated between two transformers (T1 , T2) respectively and that the respective direct link (LD) connects these two transformers in a non-isolated manner. 5. Device according to one of claims 1 to 4, characterized in that each cable is of the Ethernet cable type.