KR101142932B1 - System for preventing phising in video-telecommunication and method thereof - Google Patents

Abstract

The present invention relates to an anti-phishing technology that can determine whether a counterpart uses an alternative image instead of the actual image in a video call. The determination method disclosed by the present invention is classified as follows according to the type of the alternative image. do.

When the substitute image is a still image, when the selected frame (specific frame) among the counterpart image frames and the frame before the specific frame are the same, it is determined that the counterpart image is the substitute image.

If the substitute image is a video, the modulation frame generated by color modulation the frame is transmitted to the other party, and if there is no color change corresponding to the color modulation between the frame received from the other party and the previous frame of the frame, the other party's image is displayed. It is judged that it is a substitute image.

According to the present invention, in the case of a video call, the receiver side can determine the deceptive behavior of the counterpart through the alternative video, and can actively cope with phishing.

Video call, alternate video, phishing, phishing

Description

System for preventing phising in video-telecommunication and method

The present invention relates to a technique for preventing phishing during a video call. In particular, the present invention relates to a video call service by determining whether a counterpart is intentionally using a substitute image, for example, a still image or a video of another person, which is not a real image. The present invention relates to a method and a system for preventing phishing, which is a weak point of.

Recently, techniques for ensuring privacy and security during a video call are required. In this regard, the receiver does not send his / her own video to the caller before starting the video call after checking the video of the caller in advance, or when the caller attempts to connect the call, provides the caller's terminal with an input screen for identification. Has been proposed to check whether a call is made after checking the input value transmitted from the caller.

However, the above-described prior art only takes 'preliminary action' to prevent phishing before the video call is made, and does not consider any anti-phishing after the video call starts. That is, when the sender or the receiver acquires and uses the image (including the still image and the moving image) of a person who knows himself or someone related to the other person maliciously, the above-described precautions are useless.

Therefore, there is a need in the art for developing a technology for preventing phishing after a video call is started.

The present invention has been made to solve the above problems, and an object thereof is to provide a video call phishing prevention system and method for preventing the deception of the other party using a substitute video during the video call process.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

In the video call phishing prevention server according to an embodiment of the present invention, one specific frame received from at least one terminal among (n-1) terminals and a frame compared with the previous frame for each (n-1) terminals are compared. If there is more than one of the same terminal, the image determining unit for transmitting the warning information of the replacement image to a single terminal to determine the replacement image; And a session processor configured to terminate the session connection between the single terminal and the (n-1) terminals when determined as the substitute image. It may include.

The image determining unit may compare the entire area of the frame, compare the partial area, and compare the central area of the frame when comparing the partial area.

The video call phishing prevention server includes a frame modulator for generating a modulated frame by color-modulating the received frame; In this case, the image determining unit, after transmitting the modulation frame to one or more of the (n-1) terminals, and receives from one or more of the (n-1) terminals When one or more of the (n-1) terminals do not have a color change corresponding to the modulation frame transmission between a frame and a previous frame, warning information of a substitute image may be transmitted to the single terminal.

The frame modulator may equally up- or down-modulate each value or all values of RGB of the frame received from the single terminal to a predetermined level.

In the video call phishing prevention system according to an exemplary embodiment of the present invention, one specific frame received from at least one terminal among (n-1) terminals and a previous frame are compared with each other according to the (n-1) terminals. When there is more than one of the same terminal, anti-phishing server for transmitting the warning information of the replacement image to the single terminal to determine the replacement image; And a first call control server for establishing a session connection between the single terminal and the anti-phishing server and a second call control server for establishing a session connection between the (n-1) terminals and the anti-phishing server. Call control server; It may include.

When the phishing prevention server transmits the warning information, the session connection may be terminated between the single terminal and the (n-1) terminals through the call control server.

The anti-phishing server receives the frame from the singular terminal and generates a modulated frame by color modulation. Thereafter, the anti-phishing server transmits the generated modulation frame to one or more terminals of the (n-1) terminals and compares the received one specific frame with the previous frame for each (n-1) terminals. do. If it is determined that one or more of the (n-1) terminals do not have a color change corresponding to the transmission of the modulation frame, the anti-phishing server may transmit the warning information to the single terminal.

In the video call phishing prevention method according to an embodiment of the present invention, the (n-1) terminal is whether a specific frame received by the anti-phishing server from one or more of the (n-1) terminal is the same as the previous frame Comparing by star; And if the comparison result is the same, the anti-phishing server transmitting warning information of a substitute image to a single terminal; It may include.

In the video call phishing prevention method according to another embodiment of the present invention, a phishing prevention server generates a modulation frame by color-modulating a frame received from a single terminal, and transmits the modulation frame to one or more terminals among (n-1) terminals. step; The anti-phishing server compares a color change corresponding to the transmission of the modulation frame to one or more of the (n-1) terminals between a frame received from one or more of the (n-1) terminals and a previous frame. step; And if there is no color change, the anti-phishing server transmitting warning information of a substitute image to the single terminal; It may include.

According to another aspect of the present invention, there is provided a video call phishing prevention method, wherein any one specific frame received by the anti-phishing server from one or more of the (n-1) terminals is the same as the previous frame (n−). 1) comparing for each terminal; If the compared frames are not the same, the anti-phishing server generates a modulation frame by color-modulating a frame received from a single terminal, and transmits the modulation frame to one or more of the (n-1) terminals, and then ( n-1) comparing a color change corresponding to the transmission of the modulation frame in at least one of the (n-1) terminals between a frame received from at least one terminal of the at least one terminal and a previous frame; And when the compared frame has no color change, transmitting, by the anti-phishing server, warning information indicating a substitute image to the single terminal. It may include.

According to the present invention, since it is possible to determine the deceptive behavior of the counterpart using a substitute image such as a still image or a video during a video call, it is possible to actively cope with video call phishing.

Prior to the detailed description of the present invention, the meaning of the terms used herein will be briefly described. However, the description of terms is to aid the understanding of the present specification, and the following terms are not used to limit the technical spirit of the present invention unless the present invention is explicitly limited in the detailed description of the present invention. Be careful.

In the present specification, video call phishing means that a user intentionally or maliciously induces or hopes for the other party by storing the video (or still image) to replace his / her current video through the terminal and transmitting the video call to the other party. It may be an act.

In the present specification, when one component 'transmits' data or a signal to another component, the component may directly transmit the data or signal to the other component, and at least one other component. Through this means that the data or signal can be transmitted to the other component.

Hereinafter, a detailed description of a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted when it is deemed that they may unnecessarily obscure the subject matter of the present invention.

1 is a block diagram showing a video call phishing prevention system according to an embodiment of the present invention. 2 is a block diagram showing an anti-phishing server according to an embodiment of the present invention. Specifically, FIG. 1A is a diagram illustrating a video call phishing prevention system during a bilateral call according to an embodiment of the present invention. 1A and 2, the video call phishing prevention system 100 includes a first terminal 10, a second terminal 20, a first call control server 110, a second call control server 120, and the like. It may include an anti-phishing server 130.

The first and second terminals 10 and 20 are generally mobile terminals capable of video calls.

The first and second call control servers 110 and 120 may call and session a video call service between the first terminal 10 and the second terminal 20 connected through an access node (not shown). session) process can be performed. The first call control server 110 and the second call control server 120 and the anti-phishing server 130, if there is a request for determining the replacement image from any one of the first and second terminals (10, 20). A session may be established between the first and second terminals 10 and 20.

The session connection between the anti-phishing server 130 and the first and second call control servers 110 and 120 may include a preset session between the first call control server 110 and the second call control server 120. The session with the anti-phishing server 130 formed between the first call control server 110 and the second call control server 120 is established. More specifically, a session is established between the first terminal 10, the first call control server 110, and the anti-phishing server 130, and at the same time, the second terminal 20 and the second call control server 120. And a session may be established between the anti-phishing server 130.

The anti-phishing server 130 forwards traffic between the first and / or second terminals 10 and / or 20 to the first and / or second call control servers 110 and / or 120 after the session is established. Forwarding), and the video call service between the first and second terminals 10 and 20 may be maintained. Thereafter, the anti-phishing server 130 may determine the replacement image.

Looking at the anti-phishing server 130 in more detail with reference to Figure 2, the anti-phishing server 130 is a still image determination unit 132, frame modulator 134, video determination unit 136 and session processing unit 138 ) May be included.

The still image determining unit 132 receives a still image from the second terminal 20, and then selects one frame selected from the received frames (hereinafter, a 'specific frame') and the second terminal 20 after a predetermined time elapses. It may be determined by comparing whether there is a same frame over a specific frame and the entire area among the frames received from the. If there is the same frame as the determination result, the still image determination unit 130 may transmit warning information that the still image transmitted by the second terminal 20 is a substitute image to the first terminal 10.

The frame modulator 134 may generate a modulated frame by color-modulating at least one of the frames received from the first terminal 10.

The video determining unit 136 transmits the modulation frame generated by the frame modulator 134 to the second terminal 20 and receives a video from the second terminal 20 corresponding to the transmission of the modulation frame. After receiving the video, the video determining unit 136 compares the current frame received from the second terminal 20 with the previous frame to determine whether there is a color change corresponding to the color modulation between the current and previous frames. Can be. If there is no color change between the current frame and the previous frame, the video determining unit 136 determines that the image transmitted from the second terminal 20 is a substitute video, and alerts the first terminal 10 that the image is a substitute image. Can transmit

The session processing unit 138 transmits the request for determining the replacement image of the first terminal 10 through the first call control server 110, between the first call control server 110 and the second call control server 120. Set up a session. In detail, when there is a request for determining a substitute video of the first terminal 10, the session processor 138 sessions between the first call control server 110 and the second call control server 120 that are previously established as video call sessions. May be terminated and a session may be established between the first call control server 110, the anti-phishing server 130, and the second call control server 120.

Meanwhile, the session processor 138 determines that the image received from the second terminal 20 by the still image determining unit 132 and the moving image determining unit 136 is a substitute image, or the first terminal 10 and the second terminal. If it is determined that the video call has ended, the session connection between the set first call control server 110, anti-phishing server 130 and second call control server 120 may be terminated.

As described above, the substitute image may be a still image or a video for each type. When the substitute image is a still image, the determination of whether or not the phishing for the case of the video is described in detail with reference to FIGS. 3 to 6.

On the other hand, for convenience of description, the first terminal 110 will be set as a terminal (request terminal) that has requested a replacement image determination, but the present invention is not limited thereto. For example, it may be the case that the second terminal 120 makes a request for determining the replacement image. In addition, the alternative image determination may be automatically executed by the anti-phishing server 130 at the same time the video call service between the terminals even if there is no request from the terminal.

1B is a diagram illustrating a video call phishing prevention system during n-person call according to an exemplary embodiment of the present invention. 1B and 2, the video call phishing prevention system 100 ′ includes a single terminal 10 ′, (n-1) terminals 20 ′, a first call control server 110, and a second terminal. It may include a call control server 120 and the anti-phishing server 130.

The singular terminals 10 'and (n-1) terminals 20' are generally mobile terminals capable of video calls.

The first call control server 110 and the second call control server 120 are a single terminal 10 'connected through a connection node (not shown) and the remaining (n-1) terminals 20' out of n. , n denotes a first call control server 110 and a second call control server 120 that perform call and session processing for a video call service between two or more natural numbers).

Since the first call control server 110 and the second call control server 120 are the same as those in FIG. 1A, the description thereof will be omitted.

In addition, the anti-phishing server 130 according to an embodiment of the present invention has the same function and configuration as in FIG. 1A except for providing a service for n persons in the service between the two, so a detailed description thereof will be omitted. do. However, the anti-phishing server 130 in FIG. 1B is a substitute image if the terminal 10 'is a substitute image of the still image or video received from one or more of the (n-1) terminal 20', alternative image It can be judged that there is.

On the other hand, as shown in Figure 1a, for the convenience of the following description, a single terminal (10 ') will be assumed as a terminal (request terminal) requesting the replacement image determination, the present invention is not limited thereto. For example, this may be the case requested by (n-1) terminals 20. Also, the alternative video determination may be automatically executed in the anti-phishing server at the same time the video call service is started between the terminals even without a request from the terminals.

3 is a flowchart illustrating an alternative still image determination process of a video call phishing prevention method according to an exemplary embodiment of the present invention. Specifically, FIG. 3A is a flowchart illustrating a process of determining an alternative still image among video call phishing prevention methods in a bilateral call according to an embodiment of the present invention.

Referring to FIGS. 1A, 2, and 3A, in response to a request for determining a replacement image of the first terminal 10, the anti-phishing server 130 selects one frame selected from the frames received from the second terminal 20. Hereinafter, a temporary frame is temporarily stored (S101), and among the frames received from the second terminal 20 after a predetermined time elapses, it is determined whether the same frame is identical to the specific frame over the entire region. 132 to compare and determine (S103, S105). In the present invention, the frame after a predetermined time elapses may be a frame immediately after receiving a specific frame, and may be a frame after n seconds (n is a natural number of 1 or more). In addition, in an embodiment of the present invention, when the video call between terminals follows the Motion Picture Experts Group 4 (MPEG4) standard, 'I-Frame' may be selected as the specific frame, but the present invention is not limited thereto. .

In another embodiment of the present invention, it will be apparent to those skilled in the art that the frame received from the second terminal 20 may be determined in comparison with the specific frame before a predetermined time elapses.

As a result of determination, when the frames of the entire area are the same in step S105, the still image determining unit 132 determines that the image of the second terminal 20 is an alternative still image, and alerts the first terminal 10 to the warning information. It transmits (S107).

On the other hand, even if the frames of the entire region determined in step S105 are not the same, the case where the partial region of the frame, preferably the central region is the same, cannot be overlooked.

More specifically, the terminal user's face is generally located in the center area of the frame. Since the user of the second terminal 20 holds the terminal by hand during a video call, it is difficult to fix an image captured by the user of the second terminal 20 as a subject. That is, each of the frames of the image photographed through the second terminal 20 means that the central regions thereof may not be identical to each other.

In consideration of this, when the comparison result of the entire frame region in step S105 is not the same, the still image determination unit 132 may perform a partial region of the specific frame among the frames received from the second terminal 20 after a predetermined time. It is determined whether there is the same frame (S109, S111).

If the partial region is the same as the result of the determination, the still image determination unit 132 transmits the warning information to the first terminal 10 (S113). According to an embodiment of the present invention, a partial region of the frame may be a central region of the frame. Receiving the warning information, the first terminal 10 outputs to the user in at least one form of audio and video (including text), indicating that the other party (user of the second terminal) uses a still image as a substitute image. You can notify the user.

On the other hand, if not all areas are the same as the result of the determination, the still image determination unit 132 ends the video call to determine whether all the last frames are confirmed between the first terminal 10 and the second terminal 20. It can be determined whether or not (S115).

If the video call is not terminated as a result of the determination, the still operation determination unit 132 may return to step S103 and repeat steps S103 to S115. On the contrary, when the determination is terminated, it is no longer necessary to determine whether there is the same frame (the whole region or the partial region) between both terminals (between the first terminal 10 and the second terminal 20). The unit 132 may terminate the series of processes by terminating the session connection between both terminals through the session processing unit 138.

Meanwhile, in an embodiment of the present invention, the determination of whether the frames are identical may be made with respect to one or more of the entire region and the partial region. For example, both may be implemented to increase the accuracy of the determination, or may be implemented only for some areas in consideration of the improvement of the processing speed.

Meanwhile, FIG. 3B is a flowchart illustrating a process of determining an alternative still image among video call phishing prevention methods during n-person call according to an exemplary embodiment of the present invention. Referring to FIGS. 1A, 2 and 3B, since the same process as that of FIG. 3A is performed, a detailed description thereof will be omitted. However, FIG. 3B differs from FIG. 3A in that the first terminal 10 is replaced with a single terminal 10 'and the second terminal 20 is replaced with the remaining (n-1) terminals 20'. Therefore, if a still image received from at least one of the (n-1) terminals 20 'has a substitute image in an entire region or a partial region of the frame, there is only a difference that can be determined to have a substitute image. .

4 is a flowchart illustrating a process of determining an alternative video among video call phishing prevention methods according to an exemplary embodiment of the present invention.

4A is a flowchart illustrating a process of determining an alternative video in a video call phishing method for bilateral calls according to an embodiment of the present invention. 1A, 2, and 4A, according to a request for determining a substitute image of the first terminal 10, the anti-phishing server 130 frames at least one of the frames received from the first terminal 10. Color modulation is performed through the modulator 134 to generate a modulated frame (S201), and the video is transmitted to the second terminal 20 through the video determination unit 136 (S203).

On the other hand, 'color modulation' is a so-called 'light change' method of raising or lowering all RGB (Red, Green, Blue) values of pixels constituting the image frame to a predetermined level. The 'color change' method of increasing or decreasing can be applied. Of course, the present invention is not limited to the above-described method, and a method of raising or lowering at least one of the RGB values of the pixel to a predetermined level is also applicable.

After the step S203, the video determination unit 136 of the anti-phishing server 130 receives a frame from the second terminal 20 (S205), which is a frame in which the above-described illumination or color is modulated (hereinafter, 'Modulation frame') may be reflected.

5 is shown to illustrate this. That is, FIG. 5 is a diagram illustrating a concept of determining a substitute video in a video call phishing prevention method according to an exemplary embodiment of the present invention. Referring to FIG. 5, the modulation frame transmitted to the second terminal 20 may be incident (incident light) 1 onto the face through the screen display unit D. FIG. Subsequently, an image taken by the camera C of the second terminal 20 may reflect the influence of the reflected light 2 due to the incident light 1.

Referring back to FIG. 4, the video determination unit 136 of the anti-phishing server 130 compares the current frame n and the previous frame n-1 of the second terminal 2 received in step S205. In step S207, it is determined whether there is a color change corresponding to the color modulation in step S201 (S209).

As a result of determination, if there is no color change between the current frame n and the previous frame n-1, the video determining unit 136 considers the video transmitted from the second terminal 20 to be a replacement video, 1 transmits the warning information to the terminal 10 (S211). Receiving the warning information, the first terminal 10 may deliver the warning information of the substitute image to the user by outputting an audio or video signal as described above.

On the other hand, when there is a color change between frames corresponding to the color modulation result, the video determining unit 136 determines whether the image is checked to the last frame between the first terminal 10 and the second terminal 20. It may be determined whether the call has ended (S213).

If the video call is not terminated as a result of the determination, the video determining unit 136 may return to step S205 and repeat steps S205 to S213. On the contrary, when the video call is already terminated as a result of the determination, the frame (full area or partial area) in which the color corresponding to the color modulation between the two terminals (between the first terminal 10 and the second terminal 20) is changed is no longer present. Since it is unnecessary to determine whether there is a video, the video determining unit 136 may terminate the series of processes by terminating the session connection between the terminals 10 and 20 through the session processing unit 138.

Meanwhile, FIG. 4B is a flowchart illustrating a process of determining an alternative video among video call phishing methods during n-person call according to an exemplary embodiment of the present invention. 1B, 2 and 4B, the same process as that of FIG. 4A is developed, but the first terminal 10 is the singular terminal 10 'and the second terminal 20 is the remaining (n-1) There is a difference that is replaced by the terminal 20 '.

Accordingly, the frame modulator 134 of the anti-phishing server 130 modulates the frame received by the single terminal 10 '(S201') and transmits the same to the (n-1) terminals 20 '(S203). ').

The video determining unit 136 of the anti-phishing server 130 transmits (n-1) the modulation frames transmitted to the (n-1) terminals 20 'to each user of the terminal 20', When each terminal 20 'captures the reflected frame with the camera C (see FIG. 5) and retransmits it to the anti-phishing server 130 (S205'), the anti-phishing server 130 (n- 1) The received frame n for each of the 20 terminals 20 'is compared with the previous frame n-1 (S207') to determine whether there is an interframe change corresponding to the modulation (S209 ').

As a result of determination, if at least one of the (n-1) terminals 20 'has no color change between the current frame n and the previous frame n-1, the video determining unit 136 may (n -1) The warning information is transmitted to the single terminal 10 'by considering that at least one of the images transmitted from the number of terminals 20' is a substitute video (S211 '). The terminal 10 ′ having received the warning information may output the voice information to the user as described above. On the other hand, if there is a color change between the frames corresponding to the color modulation result, the video determining unit 136 is to determine the last frame between the singular terminal 10 'and (n-1) terminal 20' In order to determine whether all the checks are made, whether or not the video call is terminated may be determined (S213 ′). Here, whether the video call is terminated may be determined by corresponding to the n-1 number as 1: (n-1) between the single terminal device 10 'and the (n-1) terminal 20'.

As a result of the determination, if at least one of the (n-1) terminals 20 'does not end the video call, the video determining unit 136 may return to step S205' and repeat steps S205 'to S213'. On the contrary, when all the video calls are already terminated between the single terminal 10 'and the (n-1) terminals 20' as a result of the determination, the terminal is no longer between the two terminals (the single terminal 10 'and the (n-1). It may not be necessary to determine whether there is a frame in which the color corresponding to the color modulation between)) (20 ') is changed. Therefore, in this case, the video determining unit 136 may terminate the series of processes by terminating the session connection between both terminals through the session processing unit 138.

6 is a flowchart illustrating an entire process of a video call phishing prevention method according to an exemplary embodiment of the present invention. The present invention may selectively implement the above-described alternative still image determination process and the alternative video determination process, and may implement all of these processes as illustrated in FIG. 6.

In detail, FIG. 6A is a flowchart illustrating an entire process of a video call phishing prevention method in a bilateral call according to an embodiment of the present invention.

In FIG. 6A, reference numeral S100 denotes a substitute still image determination process, and S200 denotes a substitute video determination process. In other words, step S200 may be performed regardless of whether the specific frame and the frame received from the second terminal are the same in step S100, or if it is not the same as the result of step S100, step S200 may be performed.

6B is a flowchart illustrating an entire process of a video call phishing prevention method during n-person call according to an exemplary embodiment of the present invention.

6B is the same process as that of FIG. 6A, but the first terminal 10 is replaced with a single terminal 10 ′, and the second terminal 20 is replaced with the remaining (n-1) terminals 20 ′. There is only. Therefore, detailed description thereof will be omitted.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which are also implemented in the form of carrier waves (eg, transmission over the Internet). It also includes.

The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. And functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

As described above, the specification and the drawings have been described with respect to the preferred embodiments of the present invention, although specific terms are used, it is only used in a general sense to easily explain the technical contents of the present invention and to help the understanding of the invention. It is not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

The video call phishing prevention technology of the present invention can determine the deception behavior of the counterpart using the alternative video, and can actively cope with phishing which is a weak point of the current video call service.

In addition, it can contribute to the expansion of related businesses based on video call service by ensuring transparency among users.

1 is a block diagram showing a video call phishing prevention system according to an embodiment of the present invention.

2 is a block diagram showing an anti-phishing server according to an embodiment of the present invention.

3 is a flowchart illustrating an alternative still image determination process of a video call phishing prevention method according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a process of determining an alternative video among video call phishing prevention methods according to an exemplary embodiment of the present invention.

5 is a diagram illustrating a concept of determining a substitute video in a video call phishing prevention method according to an exemplary embodiment of the present invention.

6 is a flowchart illustrating an entire process of a video call phishing prevention method according to an exemplary embodiment of the present invention.

Description of the main parts of the drawing

10: first terminal 20: second terminal

100: video call system 110: the first call control server

120: second call control server 130: anti-phishing server

132: still image determining unit 134: frame modulator

136: video judgment unit

Claims (8)

Anti-phishing server for video calls between multiple terminals, By comparing one specific frame received from each terminal and the previous frame for each of the plurality of terminals, the same specific frame is determined as a substitute image, and the warning information of the substitute image is transmitted to the terminal that has requested the determination of the substitute image among the plurality of terminals. An image determining unit for transmitting; And A session processor configured to terminate the session connection between the terminal requesting the replacement image determination and the terminal transmitting the substitute image when the image is determined as the substitute image; Video call phishing prevention server, comprising a. The method of claim 1, wherein the image determining unit, And comparing the entire area of the frame, comparing the partial area, and comparing the central area of the frame when comparing the partial area. The method of claim 1, A frame modulator configured to generate a modulated frame by color-modulating the frame received from the terminal requesting the replacement image determination; More, The image determining unit, after transmitting the modulation frame to at least one terminal of the plurality of terminals, when there is no color change corresponding to the transmission of the modulation frame between the frame received from at least one terminal of the plurality of terminals and the previous frame , The video call phishing prevention server, characterized in that for transmitting the warning information of the replacement video to the terminal requesting the determination of the replacement video. The method of claim 3, wherein the frame modulator, The video call anti-phishing server, characterized in that the same or up-modulated modulation of each value or all values of the RGB of the frame received from the terminal requesting the determination of the substitute image to a predetermined level. Anti-phishing system for video calls between multiple terminals, By comparing one specific frame received from each terminal and the previous frame for each of the plurality of terminals, the same specific frame is determined as a substitute image, and the warning information of the substitute image is transmitted to the terminal that has requested the determination of the substitute image among the plurality of terminals. Anti-phishing server for transmitting; And A call comprising a first call control server for establishing a session connection between the terminal and the anti-phishing server requesting the alternative video determination, and a second call control server for establishing a session connection between the plurality of terminals and the anti-phishing server. Control server; Including; The anti-phishing server system, characterized in that when the transmission of the warning information, the session connection between the terminal and the plurality of terminals requesting the determination of the alternative video via the call control server is terminated. In the anti-phishing method in the video call between a plurality of terminals, Comparing, by the anti-phishing server, one specific frame received from each terminal with the previous frame for each of the plurality of terminals; And Determining, by the comparison frame, a substitute image for the same frame, and transmitting, by the anti-phishing server, warning information of the substitute image to a terminal that has requested a determination of the substitute image among a plurality of terminals; Video call phishing prevention method comprising a. In the anti-phishing method in the video call between a plurality of terminals, Generating, by the anti-phishing server, the modulation frame by color-modulating the frame received from the terminal requesting the replacement image determination, and transmitting the modulation frame to one or more terminals of the plurality of terminals; Comparing, by the anti-phishing server, one specific frame received from each terminal with the previous frame for each of the plurality of terminals and comparing whether there is a color change corresponding to the transmission of the modulation frame; And If there is no color change, the anti-phishing server transmitting warning information of a substitute image to the terminal requesting the determination of the substitute image; Video call phishing prevention method comprising a. In the anti-phishing method for a video call between a plurality of users, Comparing, by the anti-phishing server, one specific frame received from each terminal with the previous frame for each of the plurality of terminals; If the compared frames are not the same, the phishing prevention server generates a modulation frame by color-modulating the frame received from the terminal requesting the replacement image determination, and transmits the modulation frame to one or more terminals of the plurality of terminals. Comparing whether there is a color change corresponding to the modulation frame transmission between a frame received from at least one terminal of the terminal and a previous frame; And Transmitting, by the anti-phishing server, warning information indicating a substitute image to the terminal that has requested the determination of the substitute image when the compared frame has no color change; Video call phishing prevention method comprising a.

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