JP2000354056A - Computer network system and method for controlling access to the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve safety of a private internal subnet, without restricting the utilization of services provided on the Internet at all. SOLUTION: In a computer network system, a computer 14 in a private internal subnet 12 ca freely perform access to an external network through a computer 13 in an opened subnet 11, by operating the computer 13 in the opened subnet 11 from the computer 14 in the private internal subnet 12 by making a remote control based on frame buffer transfer. In addition, the data transfer between the subnets 11 and 12 is always carried out by only making read/write transactions from the computer 14 in the subnet 12. Because of such an access asymmetry, damages can be minimized, even if external intruders try to transfer unauthorized data to the private internal subnet 12 by using the computer 13 in the opened subnet 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer network system and an access control method therefor, and more particularly to a firewall construction technology for preventing unauthorized access from the Internet.

[0002]

2. Description of the Related Art Conventionally, when a local computer network in a company or a research organization is connected to the Internet and used, a firewall is installed to prevent unauthorized intrusion from the Internet.

[0003] As a typical firewall, 1)
A method in which a local computer network is connected to the Internet only by a router and the access is controlled by packet filtering of the router, and 2) the local computer network is divided into a public subnet and a private internal subnet, and the public subnet Are connected to the Internet via a router, and a public subnet and a private internal subnet are connected by another router or gateway.

[0004] The latter 2) can create a double barrier against intrusion from the outside, so that the use of services provided on the Internet is restricted to the minimum necessary, and other intrusions from the outside are restricted. By denying all access, the confidentiality of the private internal subnet can be maintained higher than in the former 1). However, on the other hand, computers in the closed internal subnet cannot freely use services provided on the Internet.

[0005]

As described above, in the conventional firewall, the services that can be provided to the user are limited when the security is strengthened. There is a problem that safety is reduced.

Further, in the conventional firewall, there is the following danger even in a configuration in which a double wall is formed against intrusion from outside as in the latter 2).

[0007] 1) If a computer in a closed internal subnet accidentally downloads and executes a file containing a virus or Trojan via the Internet, the internal information is destroyed or the internal information is lost. There was a risk of being transferred outside.

[0008] 2) When a computer in the public subnet is used illegally, a large amount of packets are sent in accordance with the TCP / IP protocol, thereby increasing the load on the computer in the private internal subnet and making it unusable. A denial of service attack that could

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and enables a private internal subnet to be isolated from an external network without completely restricting the use of services provided by an external network such as the Internet. It is an object of the present invention to provide a computer network system having high convenience and high security and an access control method therefor.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention divides a public subnet connected to an external network into a private internal subnet that receives services of the external network via the public subnet. Connection means for connecting between the public subnet and the private internal subnet using a communication path in which a read transaction and a write transaction are defined, and a computer in the private internal subnet and Remote operation for remotely controlling a computer in the public subnet from a computer in the non-public internal subnet using a frame buffer transfer for sharing screen information and input information so that network services can be used. Means, the remote control hand It is a remote operation using the frame buffer transfer, and executes the read transaction and the write transaction to the computer in the public subnet from the computer within said closed inner subnet.

In this computer system, the computers in the non-public internal subnet can freely access the external network through the computers in the public subnet by operating the computers in the public subnet by remote control based on the frame buffer transfer. Can be. Also,
Since the public subnet and the private internal subnet are connected using a communication path in which read transactions and write transactions are defined, basically, computers from the public subnet to computers in the private internal subnet are connected. Is transferred by a computer in a private internal subnet polling a computer in a public subnet by a read transaction at regular intervals, for example, and transferring data by a read transaction only when there is read data. Data transfer from a computer in the internal subnet to a computer in the public subnet is performed by a write transaction.
As described above, data transfer between the public subnet and the private internal subnet is always performed only by a transaction from a computer in the private internal subnet. By realizing the above-mentioned remote control by such asymmetric access, even if an outside intruder illegally uses a computer in the public subnet to transfer unauthorized data to the private internal subnet, damage will occur. Can be minimized. Therefore, the private internal subnet can be isolated from the external network without completely restricting the use of services provided by the external network such as the Internet, and a new convenient and highly confidential firewall is constructed. Can do things.

When data is shared between a computer in the public subnet and a computer in the private internal subnet, a block device is connected to a communication path on the public subnet side, and the block device is connected from the private internal subnet. For packets to the public subnet, allow all packets associated with the read and write transactions to pass through, and for packets from the public subnet to the private internal subnet, all packets from the block device, It is preferable to perform packet filtering so as to permit passage of only a read response packet for responding to a read transaction. In this case, if a computer in the public subnet is used illegally by an intruder from outside, there is a risk of writing illegal data to the block device, but since the block device itself does not execute programs, You cannot access a private internal subnet through a block device. Therefore, it is possible to share data between the public subnet and the private internal subnet while maintaining the confidentiality within the private internal subnet.

The same configuration can be applied to a case where a block device is connected to a communication path on the closed internal subnet side.

Further, screen information updated when an external user terminal remotely operates a computer in the public subnet using the frame buffer transfer via an external network such as the Internet, and By comparing the screen information registered in advance with the computer, the authentication means for causing a computer in the closed internal subnet to execute user authentication for checking the validity of the user terminal, and the authentication means When the validity of the user terminal is confirmed, the computer in the non-public internal subnet is logged out of the block device so that the user terminal can access the block device via the computer in the public subnet. From a computer in the public subnet By and means for permitting access to, it is possible to access and use the data of the computer in the private internal subnet from the outside.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a configuration of a computer network system according to a first embodiment of the present invention.
This computer network system is a local computer network system used in a company or a research institution, and has a public subnet 11 and a private internal subnet 12.
And is divided into: The public subnet 11 is a public network that can freely access the Internet.
7 is connected. Each computer 13 in the public subnet 11 is connected to a LAN such as Ethernet, and can be connected to the Internet 17 via the LAN and a router 16. Between each computer 13 in the public subnet 11 and between the computer 13 and the Internet 1
Communication with other computers on 7 is performed based on the TCP / IP protocol. In this case, public subnet 1
Each computer 13 in 1 can directly communicate with a computer on the Internet 17 at the level of the IP address.

The closed internal subnet 12 is an internal network isolated from the Internet 17, and services provided by the Internet 17 are received via the public subnet 11. Each computer 14 in the private internal subnet 12 and each computer 13 in the public subnet 11 are connected not via Ethernet but via a communication path composed of an IEEE 1394 serial bus. In other words, each computer 13 in the public subnet 11 has a communication interface for connecting to the Ethernet,
It has a communication interface for connecting to an E1394 serial bus.

A router 15 is inserted into the IEEE 1394 serial bus so as to be located between the public subnet 11 and the private internal subnet 12. Router 1
Reference numeral 5 denotes a computer provided in the private internal subnet 12 and a computer 14 in the public subnet 11 for preventing unauthorized entry into the private internal subnet 12 from outside via the public subnet 11. 13 is filtered. IEEE
Each of the computers 13, 1 to connect to the 1394 serial bus
4 has a function of automatically generating a source ID by hardware, so that the bucket filtering by the router 15 is basically performed by:
This is performed based on the transmission source ID. Due to the packet filtering function of the routers 15 and 16, the private internal subnet 12 will be protected by a double wall.

The IEEE 1394 serial bus is a communication path in which a write transaction and a read transaction are defined as communication protocols. In this embodiment, data transfer between the computer 13 in the public subnet 11 and the computer 14 in the private internal subnet 12 is performed by the computer 14 in the private internal subnet 12 to the computer 13 in the public subnet 11. By issuing a write transaction and a read transaction, the transaction is always performed under the initiative of the computer 14 in the closed internal subnet 12. A) The data transfer from the computer 13 in the public subnet 11 to the computer 14 in the private internal subnet 12 is performed by the computer 14 in the private internal subnet 12 reading the computer 13 in the public subnet 11 at regular intervals. Polling, and data transfer is performed by a read transaction only when there is read data.

B) Data transfer from the computer 14 in the closed internal subnet 12 to the computer 13 in the public subnet 11 is performed by a write transaction.

As described above, due to the asymmetry of access in which all data transfer is performed by a read / write transaction from the computer 14 in the private internal subnet 12, 1) a large amount of illegal data from the computer 13 in the public subnet 11 Even if data transfer occurs, the effect does not immediately occur on the computers 14 in the closed internal subnet 12.

2) An abnormal transfer can be detected by checking the data transfer amount at the time of polling from the computer 14 in the closed internal subnet 12.

As a result, even if the computer 13 in the public subnet 11 is illegally used by an outside intruder, the security in the private internal subnet 12 can be ensured.

Further, in this embodiment, in order to enable the use of the Internet service from the computer 14 in the private internal subnet 12, the computer 13 in the public subnet 11 is connected to the computer 14 in the private internal subnet 12. A remote control function for remote control is provided. This remote control function is performed based on frame buffer transfer. In the remote operation based on the frame buffer transfer, the screen information and the input information are shared between the computer 13 in the public subnet 11 to be operated and the computer 14 in the private internal subnet 12 to be operated, and The operation is performed by controlling the operation of the computer 13 in the public subnet 11 based on the input information from the computer 14 in the internal subnet 12, and is realized by the following mechanism.

(Sharing of Screen Information) The remote computer to be operated (here, the computer 1 in the public subnet 11)
3) The information of the frame buffer of the graphic control unit is transferred to the local computer on the operation side (here, the computer 14 in the closed internal subnet 12) via the network, and the information of the frame buffer is displayed on the local computer on the monitor. To share screen information. In this case, on the local computer, resources on the remote computer can be treated as if they existed on the local computer.

(Sharing of Input Device) Information input from the input device (keyboard, mouse) of the local computer (the computer 14 in the closed internal subnet 12 in this case) on the operation side is operated via the network. Remote computer (here, computer 1 in public subnet 11)
3), and the remote computer shares the input device by recognizing the input information from the local computer as the input information from the input device connected to the remote computer.

Remote operation by frame buffer transfer is as follows.
It can be realized by an application program. In this case, usually, the remote operation application program executed on the remote computer to be operated is the server, and the remote operation application program executed on the local computer on the operation side is the client. Sharing of screen information based on frame buffer information has low dependence on an operating system (OS) or a window system running on a remote computer, and remote operation is possible even if the OS differs between the remote computer and the local computer. It has the feature that multi-platform can be easily realized. As an application program for remote operation based on such frame buffer transfer, VNC (VNC) and the like are known.

In this embodiment, the private internal subnet 1
From the computer 14 in the public subnet 11 to the computer 1 in the public subnet 11
3 is remotely operated by frame buffer transfer, and the communication protocol for this remote operation is implemented only by a read transaction and a write transaction from the computer 14 in the closed internal subnet 12. That is, in the present embodiment, the read transaction and the write transaction from the computer 14 in the closed internal subnet 12 are used only for setting the execution environment of the remote control application program, and are restricted so that they cannot be used for other purposes. ing. Specifically, the following control is performed.

(A) On the IEEE 1394 serial bus, which is a communication path connecting the public subnet 11 and the private internal subnet 12 connected to the Internet, the computer 13 in the public subnet 11 is replaced by a computer in the private internal subnet 12. Only the communication necessary for remote operation by frame buffer transfer from 14 is performed by the above-described read transaction and write transaction, and other communication such as IP-based communication is set not to be performed.

(B) Normally, work is performed on the computer 14 in the closed internal subnet 12, and various services provided on the Internet are used by remotely operating the computer 13 in the public subnet 11 based on frame buffer transfer. I do.

According to such a use form, even if an intruder from outside illegally transfers unauthorized data to the closed internal subnet 12 using the computer 13 in the open subnet 11, the influence is limited to the frame. It is only an application for remote operation based on buffer transfer, and does not affect information in the private internal subnet 12 at all. Therefore, security within the closed internal subnet 12 can be further ensured.

That is, communication between the public subnet 11 and the private internal subnet 12 is performed by the private internal subnet 1.
Although security can be enhanced by only performing read / write transactions from the second, the use of read / write transactions is limited to remote operation only by frame buffer transfer, so that even if illegal data is Even if it is sent to the computer 14 in 12, the effect can be minimized.

Next, the filtering function of the router 15 will be described with reference to FIG.

The router 15 basically allows only packets necessary for remote control based on frame buffer transfer to pass, and blocks other packets. That is, the router 15 allows all packets accompanying the read / write transaction to pass from the computer 14 in the closed internal subnet 12 to the computer 13 in the public subnet 11, while the computer 15 in the public subnet 11 13 from the computer 14 in the private internal subnet 12, only the read response packet for responding to the read transaction from the computer 14 in the private internal subnet 12 is permitted to pass. It is set so as to block read / write request packets.

FIG. 3 shows a state of a read / write transaction executed on the IEEE 1394 bus.

The read / write transaction used in this embodiment is based on the IEEE 1394 asynchronous transfer protocol. As shown in FIG. 3A, in the read transaction, first, the computer 14 in the closed internal subnet 12 sends the public subnet 11
A read request packet is sent to the computer 13 within the public subnet 11, whereby an acknowledge (ACK) is returned from the computer 13 within the public subnet 11. Thereafter, the computer 13 in the public subnet 11 transmits a read / response packet to the computer 14 in the private internal subnet 12. The read response packet is a response packet to the read request packet, and data requested by the read request packet is transferred by the read response packet. As a result, the computers 14 in the closed internal subnet 12 communicate with the public subnet 1
1 can receive necessary data from the computer 13.

As shown in FIG. 3B,
For light transactions, the private internal subnet 1
From the computer 14 in the public subnet 11 to the computer 1 in the public subnet 11
3, a write request packet is sent. This write request packet contains write data, and can send data to the computer 13 in the public subnet 11.

In general, in a communication protocol used in a computer network, a data transfer source always performs data transfer under the initiative of a computer.
Although the second method is used, in the present embodiment, the IEEE 1394 in which the read transaction and the write transaction are defined as the communication protocol as described above is used.
By using the bus, asymmetric access control is realized, in which the computer 14 in the closed internal subnet 12 always communicates with the computer 13 in the public subnet 11 under the initiative of the computer 14. Note that any communication path other than the IEEE 1394 bus can be used as long as the communication protocol defines a read transaction and a write transaction as the communication protocol.

FIG. 4 shows a hierarchical structure of a communication protocol for implementing access control according to the present embodiment in comparison with a hierarchical structure of a communication protocol used in an ordinary computer network.

As shown in FIG. 4A, in the present embodiment, hardware such as an IEEE 1394 bus and a communication interface connected thereto are located at the lowest layer, and on top of this, hardware control is performed. Drivers, a transport protocol layer for controlling write / read transactions, and an application layer. In the application layer, an application program for remote operation based on frame buffer transfer is executed, and communication for the remote operation is realized by only a write / read transaction on the IEEE1394 bus by the transport protocol layer.

The computer 13 in the public subnet 11
FIG. 4 (b) shows other communications besides communications between the Internet and the computer 14 in the closed internal subnet 12, such as communications between the computers 13 in the open subnet 11 and communications between the computer 13 and the Internet 17. TCP / IP like
Under a normal communication environment.

Next, a remote control procedure based on frame buffer transfer will be described with reference to FIG. FIG. 5A shows how input information is transferred, and FIG. 5B shows how frame buffer information is transferred.

As described above, the remote operation application (server) is executed on the computer 13 in the public subnet 11 and the remote operation application (client) is executed on the computer 14 in the closed internal subnet 12. Is done. On the screen of the computer 14 in the closed internal subnet 12, the computer 1 in the public subnet 11 is displayed.
3 is displayed, and in this state, a keyboard operation and a mouse operation for operating the desktop screen of the computer 13 are not disclosed to the internal subnet 1.
When the processing is performed by the computer 14 in 2, the remote control application (client) recognizes that the event is a remote control input event. In this case, in response to a request from the application (client), a write transaction for transmitting input information from the computer 14 in the closed internal subnet 12 to the computer 13 in the public subnet 11 is executed (FIG. 5A). . This write transaction is executed every time an input event occurs on the computer 14 side in the closed internal subnet 12.

As described above, the information for remotely controlling the computer 13 in the public subnet 11 is transferred from the computer 14 in the private internal subnet 12 to the computer 13 in the public subnet 11. The computer 13 in the public subnet 11 is a remote control application (server).
Operates according to the input information from the computer 14 to perform various communications via the Internet 17.

The frame buffer information (screen information) of the computer 13 in the public internal subnet 11 is updated when the computer 14 in the private internal subnet 12 is polled by a read transaction at regular time intervals and the frame buffer information is updated. (FIG. 5B), whereby the screen information of the computer 13 updated by the remote operation is transferred to the computer in the closed internal subnet 12 only by performing the data transfer of the updated frame buffer information by the read transaction. Since it is sent to the computer 14 at any time, the result of the Internet service executed by the computer 13 by remote control can be confirmed on the computer 14.

(Second Embodiment) FIG. 6 shows a second embodiment of the present invention.
1 shows a configuration of a computer network system according to an embodiment. The system configuration of this computer network system and the access control method for remote operation are described in the first section.
Since this embodiment is basically the same as the embodiment, only different portions will be described below.

That is, in FIG. 6, a block device 21 is provided on the public subnet 11 side for the purpose of sharing data between the computer 13 in the public subnet 11 and the computer 14 in the private internal subnet 12. . The block device 21 is a data storage device that inputs and outputs data in units of a data block composed of a plurality of bytes.
A drive, MO, magnetic tape, or the like is used. The block device 21 is connected to the IEEE 1394 bus of the router 15 on the public subnet 11 side as shown in FIG.
It can be freely accessed from the computer 13 in the public subnet 11.

The block device 21 is provided with a control mechanism for transferring data only when the source ID of the access request and the data transfer source or data transfer destination ID match.

Next, the filtering function of the router 15 will be described with reference to FIG.

In the second embodiment, not only from the computer 13 in the public subnet 11, but also from the computer 14 in the private internal subnet 12, the block device 21
, The passage restriction of the bucket by the router 15 is relaxed as compared with the first embodiment.

That is, the router 15 allows all packets accompanying a read / write transaction from the computer 14 to the computer 13 or the block device 21 to pass from the private internal subnet 12 to the public subnet 11, For packets from the public subnet 11 to the private internal subnet 12,
Only the read response packet for responding to the read transaction from the computer 14 in the closed internal subnet 12 and all the packets from the block device 21 are permitted to pass, and the read / write request packet from the computer 13 is blocked. Is set.

FIG. 8 shows a procedure when the computer 14 in the private internal subnet 12 accesses the block device 21 on the public subnet 11 side. Here, a case where data written by the computer 13 in the public subnet 11 is read from the block device 21 will be described as an example. This access procedure is SBP_2
(SBP: Serial Bus Protocol)
It is performed according to.

The block device 21 performs authentication (logi
n) It has a function, and while a computer is logging in to the block device 21, access from another computer is not accepted. For this reason, when using the block device 21, the computer 14 in the closed internal subnet 12 first accesses to log in to the block device 21. For access for login, the login request is written in an ORB (operation
The block is created in the main memory of the computer 14 in the form of (request block), and is executed by performing a write transaction for writing the address of the ORB to the MANAGEMENT_AGENT register of the block device 21. The block device 21 reads the ORB for the login request by the read transaction.
Is read, and if the login is permitted based on whether or not the password matches the password registered in the block device 21 in advance, the block device 21 returns a response to that effect. In this way, when the login is successful, the computer 14 in the closed internal subnet 12 creates a request to the block device 21 in the main memory of the computer 14 in the form of ORB, and stores the address of the ORB in the block device 21. Execute a write transaction for writing to the ORB_POINTER register. In response to this, the block device 21 executes a read transaction for reading the contents of the ORB from the computer that has issued the access request. If the request is a data read request, the block device 21 executes a write transaction for writing the data specified by the ORB to the computer that has issued the access request. When reading of all necessary data is completed, the computer 14 in the closed internal subnet 12 creates a logout request in the main memory of the computer 14 in the form of an ORB, and stores the address of this ORB in the MANAGEMENT_
A write transaction for writing to the AGENT register is executed, and the user logs out of the block device 21.

As described above, in the second embodiment,
(A) Between public subnet 11 and private internal subnet 1
2 is connected to an IEEE 1394 serial bus, which is a communication path having a standard for automatically generating a source ID by hardware, via a router 15 having a function of performing packet filtering based on the source ID. , (B)
A block having a control mechanism on the side of the public subnet 11 that can be used by connecting to the network and transfers data only when the source ID of the access request is equal to the data transfer source / destination ID specified by the ORB. Device 21
(C) all packets from the private internal subnet 12 to the public subnet 11 pass through, and from the public subnet 11 to the private internal subnet 12, all packets from the block device and read / response packets from the computer 13 By setting the router 15 so that only the data passes through, the data sharing between the public subnet 11 and the private internal subnet 12 is realized via the block device 21.

When a computer 13 in the public subnet 11 is illegally used by an intruder from outside, there is a risk that unauthorized data may be written to the block device 21, but the block device 21 executes a program like a computer. There is no function, and the block device 21 cannot control itself to access the private internal subnet 12. Further, even if an unauthorized request is written to the block device 21, it is impossible to transfer the request to the computer 14 in the closed internal subnet 12 by the function (b). Therefore, the data of the block device 21 can be shared between the public subnet 11 and the private internal subnet 12 while keeping the confidentiality in the private internal subnet 12.

(Third Embodiment) FIG. 9 shows a third embodiment of the present invention.
1 shows a configuration of a computer network system according to an embodiment. In this computer network system, the block device 21 for data sharing is connected to the IEEE 1394 serial bus of the router 15 on the closed internal subnet 12 side. The block device 21 can be freely accessed from the computer 14 in the closed internal subnet 12.

FIG. 10 shows a filtering function of the router 15.

That is, the router 15 transmits all packets accompanying a read / write transaction from the computer 14 to the computer 13 from the private internal subnet 12 to the public subnet 11 and from the block device 21 to the computer 13. , While packets from the public subnet 11 to the private internal subnet 12 include a read response packet for responding to a read transaction from a computer 14 in the private internal subnet 12 and a public subnet. 11 to the block device 21
Allow only packets with a specific address to pass through,
Other packets to the block device 21 and read / write request packets from the computer 13 to the computer 14 are set to be blocked.

Here, the computer 1 in the public subnet 11
3 is a packet of a specific address for the block device 21.
This is a packet for the NT_AGENT register and the ORB_POINTER register. As a result, the risk that unauthorized data is written from the computer 13 in the public subnet 11 to the block device 21 can be reduced, and the data can be shared between the computer 13 and the computer 14.

The function of the router 15 is enhanced so that the computer 13 in the public subnet 11
1 by monitoring the log-in process to 1 and passing the packet to the ORB_POINTER register only when the log-in succeeds, and providing the router 15 with a function of notifying the administrator when the log-in fails, thereby further improving the security. Can be improved. FIG. 11 shows a processing procedure of the router 15 in this case.

The router 15 constantly monitors the destination address of the packet transmitted from the computer 13 in the public subnet 11, and transmits the packet to the login address,
That is, MANAGEMENT_ of the block device 21
It is determined whether or not the packet is for the AGENT register (step S11). If the packet received from the computer 13 in the public subnet 11 is a packet addressed to the login address (YES in step S11), the router 15 passes the packet (step S1).
2). Then, the router 15 determines whether the login has succeeded based on the presence or absence of the response packet indicating the successful login from the block device 21 (step S13). If login fails, the router 15
Notifies the administrator (step S14),
Blocks packets destined for the block device from the computer 13 in the public subnet 11. If the login is successful (step S13 is YES), the router 15 proceeds to the processing after step S15, and the packet received from the computer 13 in the public subnet 11 is replaced with the address for the request from the computer that has successfully logged in. Packet to (O
A write packet for the RB_POINTER register or a logout packet (Management_A) from a computer that has successfully logged in.
If the packet is a write packet for GENT, control is performed to pass the packet and block other packets (steps S15 to S19).

As a result, unauthorized access from the public subnet 11 to the block device 21 can be reduced, and the security of the private internal subnet 12 can be further improved.

Further, the block device 21 monitors a read transaction for reading the ORB created by the computer 13 in the public subnet 11 and
1 is added to the router 15 only when the ID of the data transfer source / destination specified by the ORB is equal to the ID of the computer 13 in the ORB. It is also possible to omit the check mechanism of the transmission source ID and the data transfer source / destination ID.

(Example of Application to Second and Third Embodiments) Next, with reference to FIG. 12, a process for improving security by using the exclusive control mechanism of the block device 21 will be described. This processing procedure uses the exclusive control mechanism of the block device 21 so that the computer 14 in the closed internal subnet 12 is preferentially logged in to the block device 21, and the public subnet 11 is used only when data sharing is desired. This is an exclusive control of permitting access from a user.

That is, normally, the computer 14 in the closed internal subnet 12 logs in to the block device 21 (step S21). As a result, normally, all logins from the public subnet 11 are rejected. For example, the computer 14 in the closed internal subnet 12 is set so that the block device 21 can be automatically mounted as a remote drive.
The computer 13 in 1 may be set so as to require a remote operation from the computer 14 in the closed internal subnet 12 to log in.

When data is shared with the public subnet 11, that is, data in the public subnet 11 is transferred to the private internal subnet 12 through the block device 21.
At the time of transfer, or vice versa (step S2
2), the computer 14 in the closed internal subnet 12 that has logged in to the block device 21 temporarily logs out of the block device 21 (step S).
23). Thereafter, the computer 13 in the public subnet 11 is remotely controlled from the computer 14 in the private internal subnet 12 by using the frame buffer transfer according to the above-described procedure, so that the computer 13 in the public subnet 11 is logged into the block device 21. (Step S24).
Then, the computer 13 in the public subnet 11 is remotely controlled from the computer 14 in the private internal subnet 12 to remotely control the computer 13 in the public subnet 11 and the block device 2.
1 (step S2).
5) Perform remote control again to log out the computer 13 in the public subnet 11 from the block device 21 (step S26). Then, finally, the computer 14 in the closed internal subnet 12 re-opens the block device 2
1 (step S21). Thus, all logins from the public subnet 11 are rejected again.

(Fourth Embodiment) FIG. 13 shows the configuration of a computer network system according to a fourth embodiment of the present invention. The system configuration of this computer network system, the access control method for remote operation, and the data sharing method are the same as those of the third embodiment, but are different from those of the fourth embodiment.
In the embodiment, a remote access function is provided for enabling the external computer 100 to access data in the closed internal subnet 12 via the Internet. This remote access function is for making it possible to refer to the data of one's own computer in the office, for example, from outside or at home. In the present embodiment, a remote control application program for remotely controlling the computer 13 in the public subnet 11 by frame buffer transfer is provided by the computer 1 in the private internal subnet 12.
4 as well as the external computer 100, and a remote access function is realized by performing authentication of the external computer 100 using the operation at the time of screen sharing.

First, the basic operation in the case where the remote computer is remotely controlled by remote control from a plurality of local computers will be described. In the present embodiment, the remote computer to be operated is the computer 13 in the public subnet 11, and the local computer on the operating side is the computer 14 and the external computer 100 in the non-public internal subnet 12.

The frame buffer of the remote computer is transferred to the plurality of local computers, and the input information from the input devices of the plurality of local computers is transferred to the remote computer. The input information of each local computer is merged on the remote computer, and the operation of the remote computer is controlled based on the input information. By such a series of operations, it is possible to perform the work by sharing the screen of the remote computer on a plurality of local computers. In this case, if the operation of an input device (keyboard, mouse) of a certain local computer updates the screen, the updated frame buffer information is transferred to all other local machines sharing the same screen. become.

Therefore, in this embodiment, the external computer 10
Update frame buffer information (screen information) when predetermined input information is input from 0 is registered in advance in the computer 14 in the closed internal subnet 12, and the registration information
The user authentication method of comparing the updated frame buffer information from the computer 13 in the public subnet 11 with the computer 14 in the non-public internal subnet 12 and permitting the external computer 100 to access the internal data when they match with each other. use. Whether the internal data can be accessed is determined using the exclusive control mechanism of the block device 21.

In order to realize such a user authentication method, specifically, the following functions are added to an application program for remote operation.

(A: Recording and Reproducing Function of Input Information from Input Device (Keyboard, Mouse)) Information input to the input device is stored in a file for a remote operation application running on the local computer on the operation side. Etc.,
A function to reproduce input information based on the stored information is added. This is because the same input operation as the authentication input operation such as the mouse operation performed by the user of the local computer can be reproduced on the external computer 100 as many times as necessary.

(B: Function of Recording Updated Frame Buffer Information) A function of storing updated frame buffer information in a file or the like is added to a remote operation application operating on the local computer on the operating side. This is because the update frame buffer information for authentication is registered in the computer 14 in the closed internal subnet 12.

(C: Command execution function based on updated frame buffer information) The same updated frame buffer information as the preset updated frame buffer information is transferred to the remote operation application running on the local computer on the operating side. When a command is issued, a function to execute a certain command is added. This is because the authentication of the external computer 100 is performed by comparing the updated frame buffer information, and when the authentication is successful, the computer 14 in the closed internal subnet 12 automatically logs out of the block device 21 and the internal computer This is to allow access to data.

(D: Command execution function at the time of communication connection disconnection) The remote operation application running on the local computer as the operation side is different from the remote operation application running on the remote computer as the operation target. A function to execute a certain command when the communication connection is disconnected is added. This is because, when the access to the internal data by the external computer 100 ends, the computer 14 in the closed internal subnet 12 logs in to the block device 21 again and prohibits access from the public subnet 11 side. .

(E: Communication connection disconnection function on remote computer) Communication between the remote operation application running on the remote computer to be operated and the remote operation application running on one local computer When the connection is disconnected, a function is added to disconnect the communication connection with the remote operation application running on all the local computers sharing the screen. This is to notify the computer 14 in the closed internal subnet 12 of the end of the access to the internal data by the external computer 100.

By utilizing the above functions, it is possible to access data in the closed internal subnet 12 via the Internet in the following procedure.

First, the following processing is performed as preparation processing. (I) The computer 14 in the closed internal subnet 12 stores data that the block device 21 wants to access via the Internet.

(Ii) Computer 1 in Public Subnet 11
3 is remotely controlled from the computer 14 in the closed internal subnet 12, and the following processing is performed.

(Ii-1) Using the functions (a) and (b), a value is randomly input to the input device, and the input information from the input device and the computer 13 in the public subnet 11 are used. The updated frame buffer information sent from the server is stored in a file or the like. The input information stored in the file is used later on the external computer 100.

(Ii-2) Using the function of (c),
When the same update frame buffer information as that stored in (ii-1) is transferred, the computer 14 in the closed internal subnet 12 is set to log out of the block device 21. Also,
Using the function (d), the computer 14 in the private internal subnet 12 is set so that when the communication connection with the computer 13 in the public subnet 11 is disconnected, the user logs in to the block device 21 again. I do.

Next, a procedure for accessing data in the closed internal subnet 12 via the Internet will be specifically described with reference to FIGS. 13 and 14.

(1): Reproduction of input information (step S10)
1) The application for remote operation is executed on each of the computers 13, 14,
The input information stored in the file while being executed on the computer 100 is reproduced on the external computer 100, and the input information for authentication is input to the computer 13 in the public subnet 11.

(2): Transfer of updated frame buffer information (step S102) Since the computers 13, 14, and 100 share the screen, the screen information of the computer 13 in the public subnet 11 is updated by the input information for authentication. Then, the contents of the updated frame buffer information are sent to the computer 14 in the closed internal subnet 12. The transmission of the updated frame buffer information is executed by a read transaction by the computer 14 in the closed internal subnet 12.

(3): Logout (Step S103) The computer 14 in the closed internal subnet 12 compares the updated frame buffer information with the pre-recorded updated frame buffer information to make the external computer 10
0 user authentication is performed. When the update frame buffer information matches the pre-recorded update frame buffer information, the computer 14 in the closed internal subnet 12 temporarily stops the block device 21 to permit the external computer 100 to use the block device. Log out to

(4): Login, Data Transfer, Logout (Step S104) The external computer 100 is connected to the computer 13 in the public subnet 11.
Is remotely controlled, the user logs in to the block device 21 through the computer 13 in the public subnet 11. Then, by reading necessary data from the block device 21 by remotely operating the computer 13 in the public subnet 11, the user logs out of the block device 21 through the computer 13 in the public subnet 11.

(5): End of remote control (step S10)
5) The external computer 100 is a computer 13 in the public subnet 11
Of the remote operation of the computer 1 in the public subnet 11
3 is disconnected.

(6): Disconnection of Connection (Step S)
106) The computer 13 in the public subnet 11 is the external computer 10
In response to the disconnection of the communication connection with 0, the communication connection with the computer 14 in the closed internal subnet 12 is disconnected.

(7): Re-login (step S107) This connection disconnection causes the closed internal subnet 1
The computer 14 in 2 logs in the block device 21 again and occupies the block device 21 exclusively.

With the above processing, the data in the private internal subnet 12 can be used from outside.
Since there is a danger of eavesdropping on data being transferred on the Internet, it is preferable to encrypt data in the private internal subnet 12 in advance.

[0090]

As described above, according to the present invention,
With the ability to isolate private internal subnets from external networks without completely limiting the use of services provided by external networks such as the Internet,
A highly convenient and highly secure computer network system can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a computer network system according to a first embodiment of the present invention.

FIG. 2 is an exemplary view for explaining a packet filtering function of a router used in the first embodiment;

FIG. 3 is an exemplary view showing a state of a read / write transaction executed on a communication path connecting a public subnet and a private internal subnet according to the first embodiment;

FIG. 4 is an exemplary view for explaining a hierarchical structure of a communication protocol used in the first embodiment;

FIG. 5 is an exemplary view for explaining a remote control procedure based on frame buffer transfer executed in the first embodiment.

FIG. 6 is a block diagram showing a configuration of a computer network system according to a second embodiment of the present invention.

FIG. 7 is an exemplary view for explaining a packet filtering function of a router used in the second embodiment.

FIG. 8 is an exemplary view showing an access procedure for a block device provided in the system of the second embodiment.

FIG. 9 is a block diagram showing a configuration of a computer network system according to a third embodiment of the present invention.

FIG. 10 is an exemplary view for explaining a packet filtering function of a router used in the third embodiment;

FIG. 11 is an exemplary flowchart showing a specific procedure of a packet filtering process executed by the router according to the third embodiment;

FIG. 12 is an exemplary flowchart showing the procedure of an exclusive control process for a block device according to the second and third embodiments.

FIG. 13 is a block diagram showing a configuration of a computer network system according to a fourth embodiment of the present invention.

FIG. 14 is an exemplary flowchart showing the procedure of a remote access process in the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Public subnet 12 ... Private subnet 13 ... Computer in public subnet 14 ... Computer in private subnet 15, 16 ... Router 21 ... Block device 100 ... External computer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B089 GA21 GA31 GB03 HA06 HA10 HA18 HB02 JA35 JB22 KA17 KC58 LB04 LB14 5K030 GA15 HA08 HB06 HC01 HC14 HD03 HD06 LD20 5K033 AA08 BA04 CB01 CB08 DA06 DB12 DB16 DB19 EA07 EC04 9 CC06 CC07 CC08 DD06 JJ25 JJ27

Claims (13)

[Claims] A read transaction and a write transaction are defined in a computer network system divided into a public subnet connected to an external network and a private internal subnet that receives services of the external network via the public subnet. Connection means for connecting the public subnet and the private internal subnet using a communication path; and screen information and input so that a computer in the private internal subnet can use services of the external network. Remote control means for remotely controlling a computer in the public subnet from a computer in the closed internal subnet by using a frame buffer transfer for sharing information, the remote control means comprising: Remote control using A computer network system, which is executed by a read transaction and a write transaction from a computer in the closed internal subnet to a computer in the public subnet. 2. A packet filtering means inserted into the communication path so as to be located between the public subnet and the private internal subnet, and filtering packets transmitted and received between the private internal subnet and the public subnet. The packet filtering means, for a packet from the private internal subnet to the public subnet, permits the passage of all packets accompanying the read transaction and the write transaction, and the private subnet from the public subnet 2. The computer network system according to claim 1, wherein a packet to an internal subnet is permitted to pass only a read response packet for responding to the read transaction. 3. A communication system in which a read transaction and a write transaction are defined in a computer network system divided into a public subnet connected to an external network and a private internal subnet receiving services of the external network via the public subnet. Connection means for connecting the public subnet and the private internal subnet using a network, screen information and input information so that a computer in the private internal subnet can use the service of the external network. Remote control means for remotely controlling a computer in the public subnet from a computer in the closed internal subnet by using a frame buffer transfer for sharing the remote control using the frame buffer transfer, Private internal subnet Remote control means for executing read and write transactions from a computer to a computer in the public subnet, and inserted into the communication path so as to be located between the public subnet and the private internal subnet; A packet filtering means for filtering packets transmitted and received between the subnet and the public subnet; and a computer connected to the communication path on the public subnet side, the computer in the public subnet and the computer in the private internal subnet. A block device used for data sharing, wherein the packet filtering means is configured to perform a read transaction and a write transaction with respect to a packet from the private internal subnet to the public subnet. Permitting the passage of packets, and permitting the passage from the public subnet to the private internal subnet of all packets from the block device and only the read response packet for responding to the read transaction. A computer network system characterized by the following. 4. The block device is configured to prohibit access from another computer until a computer logged in to the block device logs out. Means for prohibiting a computer in the public subnet from accessing the block device by preferentially logging a computer into the block device, wherein the remote control means shares data of the block device In this case, after temporarily logging out the computer in the non-public internal subnet, remotely controlling the computer in the public subnet to access the block device from the computer in the public subnet. The computer network system according to claim 3, wherein 5. A read transaction and a write transaction are defined in a computer network system divided into a public subnet connected to an external network and a private internal subnet that receives services of the external network via the public subnet. Connection means for connecting the public subnet and the private internal subnet using a communication path; and screen information and input so that a computer in the private internal subnet can use services of the external network. Remote control means for remotely controlling a computer in the public subnet from a computer in the closed internal subnet by using a frame buffer transfer for sharing information, wherein the remote control using the frame buffer transfer is performed. The private internal subnet Remote control means for executing a read transaction and a write transaction from a computer within the public subnet to a computer within the public subnet; inserted into the communication path so as to be located between the public subnet and the private internal subnet; Packet filtering means for filtering a packet exchanged between an internal subnet and the public subnet; and a computer in the public subnet and a computer in the private internal subnet, which are connected to a communication path on the private internal subnet side. And a block device used for data sharing with the device. The packet filtering means performs a read transaction and a write transaction on a packet from the private internal subnet to the public subnet. For all packets from the public subnet to the private internal subnet, a read response packet for responding to the read transaction and access to the block device from a computer in the public subnet are allowed. A computer network system that allows only packets to pass through. 6. The block device is configured to prohibit access from another computer until a computer logged in to the block device logs out. Means for prohibiting a computer in the public subnet from accessing the block device by preferentially logging a computer into the block device, wherein the remote control means shares data of the block device In this case, after temporarily logging out the computer in the non-public internal subnet, remotely controlling the computer in the public subnet to access the block device from the computer in the public subnet. The computer network system according to claim 5, wherein 7. A communication system in which a read transaction and a write transaction are defined in a computer network system divided into a public subnet connected to an external network and a private internal subnet receiving services of the external network via the public subnet. Connection means for connecting the public subnet and the private internal subnet using a network, screen information and input information so that a computer in the private internal subnet can use the service of the external network. Remote control means for remotely controlling a computer in the public subnet from a computer in the closed internal subnet by using a frame buffer transfer for sharing the remote control using the frame buffer transfer, Private internal subnet Remote control means for executing read and write transactions from a computer to a computer in the public subnet, and inserted into the communication path so as to be located between the public subnet and the private internal subnet; A packet filtering means for filtering a packet transmitted and received between a subnet and the public subnet, wherein for a packet from the private internal subnet to the public subnet, passing of all packets accompanying the read transaction and the write transaction And for a packet from the public subnet to the private internal subnet, a read response packet for responding to the read transaction, and a computer in the public subnet Packet filtering means for permitting the passage of only packets for accessing the block device from the network device, and connected to a communication path on the side of the private internal subnet, and during a period until a computer in the private internal subnet logs out. A block device configured to prohibit access from a computer in the public subnet, and updated when an external user terminal remotely operates a computer in the public subnet using the frame buffer transfer via an external network. By comparing the screen information stored in the closed internal subnet with screen information registered in advance in a computer in the closed internal subnet, a user authentication for checking the validity of the user terminal is performed by a computer in the closed internal subnet. Authentication means to be executed by the If the validity of the terminal is confirmed, log out the computer in the non-public internal subnet from the block device so that the user terminal can access the block device via a computer in the public subnet. Means for permitting a computer in the public subnet to access the block device. 8. A public transaction connected to an external network and a private internal subnet that receives services of the external network via the public subnet, and a read transaction is performed between the public subnet and the private internal subnet. And a write transaction, wherein the access control method is applied to a computer network system connected using a communication path defined in order to enable a computer in the closed internal subnet to use a service of the external network. Remotely controlling a computer in the public subnet from a computer in the non-closed internal subnet using a frame buffer transfer for sharing screen information and input information; In the public internal subnet Access control method characterized by the calculation unit to be executed by the read transaction and the write transaction to the computer in the public subnet. 9. A public subnet connected to an external network and a private internal subnet that is served by the external network via the public subnet, and a read transaction is performed between the public subnet and the private internal subnet. A write transaction is connected by a defined communication path, and the communication path on the public subnet side is a block device used for data sharing between a computer in the public subnet and a computer in the closed internal subnet. Is an access control method applied to a connected computer network system, for sharing screen information and input information so that a computer in the closed internal subnet can use services of the external network. Frame buffer transfer Remote control by a read transaction and a write transaction from a computer in the private internal subnet to a computer in the public subnet, thereby remotely controlling a computer in the public subnet from a computer in the private internal subnet. And, for packets from the private internal subnet to the public subnet, allow all packets to pass, and for packets from the public subnet to the private internal subnet, all packets from the block device, Filter a packet transmitted and received between the private internal subnet and the public subnet so as to permit passage of only a read response packet for responding to a read transaction from a computer in the private internal subnet. Access control method, characterized by a ring. 10. The block device, wherein the block device is configured to prohibit access from another computer until a computer logged in to the block device logs out. By making a computer preferentially log in to the block device, access to the block device from computers in the public subnet is prohibited, and when sharing data of the block device, the private internal subnet is used. After temporarily logging out a computer in the public subnet, remotely controlling a computer in the public subnet from a computer in the private internal subnet to access the block device from a computer in the public subnet. The access control method according to claim 9, wherein 11. A public subnet connected to an external network and a private internal subnet that is served by the external network via the public subnet, and a read transaction is performed between the public subnet and the private internal subnet. A light transaction is connected by a defined communication path, and the communication path on the closed internal subnet side is used for data sharing between a computer in the open subnet and a computer in the closed internal subnet. An access control method applied to a computer network system to which a block device is connected, wherein screen information and input information are shared so that a computer in the closed internal subnet can use a service of the external network. Frame bar for Remote control by transfer from a computer in the private internal subnet to a computer in the public subnet by performing a read transaction and a write transaction from the computer in the private internal subnet to a computer in the public subnet from the computer in the private internal subnet. Remotely controlling, for the packet from the private internal subnet to the public subnet, permit the passage of all packets accompanying the read transaction and the write transaction, and for the packet from the public subnet to the private internal subnet, A read response packet for responding to the read transaction,
Filtering a packet exchanged between the closed internal subnet and the public subnet so as to permit only a packet for accessing the block device from a computer in the public subnet. Access control method. 12. The block device, wherein the block device is configured to prohibit access from other computers until a computer logged in to the block device logs out. By making a computer preferentially log in to the block device, prohibiting access to the block device from a computer in the private internal subnet, and sharing data of the block device, After temporarily logging out a computer in the internal subnet, remotely controlling a computer in the public subnet from a computer in the non-public internal subnet to access the block device from a computer in the public subnet. The method according to claim 11, wherein
Described access control method. 13. A public subnet connected to an external network and a private internal subnet that is served by the external network via the public subnet. A read transaction is performed between the public subnet and the private internal subnet. While the write transaction is connected by the defined communication path, the communication path on the closed internal subnet side is connected from the computer in the open subnet until the computer in the closed internal subnet logs out. An access control method applied to a computer network system to which a block device configured to prohibit access to the external network is connected, wherein a computer in the closed internal subnet can use a service of the external network. Screen information And remote operation by frame buffer transfer for sharing input information is performed by a read transaction and a write transaction from a computer in the private internal subnet to a computer in the public subnet. Remotely controlling a computer in the public subnet from a computer, for a packet from the private internal subnet to the public subnet, permitting passage of all packets accompanying the read transaction and the write transaction, and For a packet to a private internal subnet, a read response packet for responding to the read transaction,
Filtering packets exchanged between the private internal subnet and the public subnet by the router so as to permit the passage of only packets for accessing the block device from a computer in the public subnet, Screen information updated when an external user terminal remotely controls a computer in the public subnet via the network using the frame buffer transfer via a network, and screen information registered in advance in a computer in the secret internal subnet. By comparing, the user authentication for checking the validity of the user terminal is executed by a computer in the closed internal subnet, and when the validity of the user terminal is confirmed by the user authentication, The user terminal communicates via a computer in the public subnet As can access the lock device, the access control method characterized by the computer in the private internal subnet log out from the block device to allow access to the block device from a computer within the public subnet.