JP2007293643A - Email system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an email system that can prevent mail sending unintended by mail senders without overloading the mail senders. <P>SOLUTION: The email system comprises a mail client for attaching control information about mail to a signature and sending outgoing mail messages with the signature attached at mail sending, a control information server for managing the control information and determining whether or not to send mail messages according to the control information attached to the mail messages, and a mail server for receiving and sending mail messages permitted to be sent by the control information server. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic mail system that can transmit only mail intended by a sender and can prevent transmission of mail unintended by the sender.

  Generally, in an electronic mail system, a mail that the sender does not want to transmit may be transmitted. For example, in a personal computer or the like into which a malicious program such as a virus has entered, the malicious program may send a mail without permission. If the virus spreads and propagates, it may cause the email system to go down. At present, there is no effective means for preventing such mail transmission processing.

  Filtering technology has been put into practical use mainly from the viewpoint of preventing confidential leaks. This is to block the mail to be sent if the subject or body of the mail contains specific characters or phrases, or a specific file is attached, or is sent to a specific destination. It is. This technology cannot effectively block all emails sent by programs such as viruses.

As a means for preventing forwarding of mail not intended by the sender, there is a technique for preventing forwarding by adding control information to the mail (see, for example, Patent Document 1 and Patent Document 2). In addition, there is an electronic mail that gives an electronic signature and permits transmission only with an electronic signature that is allowed (see, for example, Patent Document 3). Furthermore, by sending the mail ID sent by the mail client software in advance to the mail server, and then sending the mail with that ID to the mail server, only the mail intended by the sender can be sent. There is what can be made (for example, see Patent Document 4).
JP 2000-124942 A JP 2005-141294 A JP 2004-265025 A JP 2004-104633 A

  However, in Patent Document 1 and Patent Document 2, mail transfer can be restricted, but new mail transmission cannot be completely prevented. Moreover, in the thing of patent document 3, a sender must give an electronic signature every time a mail is transmitted, and the sender is forced to perform an operation for mail transmission. Furthermore, the patent document 3 requires dedicated mail client software.

  An object of the present invention is to provide an electronic mail system that can reduce the burden on the mail sender and prevent the mail from being sent without permission from the mail sender.

  The e-mail system according to the present invention includes a mail client that attaches control information about a mail to a signature sentence and sends the signature sentence to the outgoing mail when sending the mail, manages the control information, and is attached to the mail. A control information server that performs a process for determining whether or not a mail can be transmitted based on the control information, and a mail server that receives a mail that has been determined to be transmittable by the control information server and performs a mail transmission process. And

  According to the present invention, since an automatic giving function such as a signature sentence normally provided in a mail client is used and control information related to mail is automatically embedded in a transmission mail, the burden on the mail sender is small and the sender's intention for transmission is reduced. Presence / absence can be easily determined, and mail transmission can be controlled according to the result of the determination.

  FIG. 1 is a configuration diagram of an electronic mail system according to an embodiment of the present invention. The mail server 11 performs transmission / reception processing of electronic mail with the mail client 12 and other mail servers 11, and a control information server 13 is provided between the mail server 11 and the mail client 12.

  The mail client 12 operates on the terminal 14 and is used by a mail sender to access the electronic mail system. The mail client 11 sends and receives electronic mail according to the instructions of the sender. The mail client 12 has a function of adding a signature to the mail when creating the outgoing mail or sending it to the mail server. The function of assigning a signature text is usually provided in a general mail client that is commercially available.

  The signature text is generally called a signature or the like, and this signature text contains information indicating information such as the user's name, mail address, telephone number, and affiliation, and is attached to the end of the transmitted mail. In the embodiment of the present invention, the mail client 12 only needs to have a function of giving such a signature text. Then, the mail client 12 gives control information about the mail to the signature sentence, and attaches the signature sentence to the outgoing mail when sending the mail.

  The control information generation unit 15 of the control information server 13 creates control information and stores it in the control information database 16. Further, it has a function of disclosing control information in the control information database 16 in response to an inquiry from the mail client 12 or the like.

  The control information confirmation unit 17 of the control information server 13 extracts the control information given to the mail from the mail transmitted from the mail client 12 and confirms whether the control information exists in the control information database 16. If the control information is correct, a function of transferring to the mail server 11 is provided. If the control information does not exist or is invalid, the transmission of the mail is rejected.

  In the above description, the case where the control information generation unit 15, the control information database 16, and the control information confirmation unit 17 are provided as the control information server 13 without changing the existing mail server 11 has been described. 15, the control information database 16 and the control information confirmation unit 17 may be integrally formed, or may be configured on the mail server 11. In any case, the control information generation unit 15, the control information database 16, and the control information confirmation unit 17 are formed to manage the control information as a whole and determine whether the mail can be transmitted based on the control information given to the mail. What is necessary is just to form the control information server 13 as a function which performs a determination process.

  Next, as the control information, a random character string or the like which does not appear in the mail text or signature text is used. Since it is added to the signature sentence, a character string with a length of up to several hundred characters is appropriate. Any character string that does not appear in the body of an email as a normal character string and that is not erroneously recognized as the body of an email may be used.

  FIG. 2 is a flowchart of the e-mail transmission process in the embodiment of the present invention. When creating the mail, the mail client 12 determines whether control information is set in the signature text (S1). If it is not set in the signature text, control information is obtained (S2). The control information is obtained by accessing the control information generation unit 15 of the control information server 13 and obtaining the control information. Although details of the method of accessing the control information generation unit 15 will be described later, it is obtained using a method that cannot be easily seen by others.

  Next, the obtained control information is attached to the signature of the mail client (S3), and a mail is created using the mail client 12 (S4). On the other hand, if the control information has already been set in the signature text in the determination in step S1, a mail is created using the mail client 12 as it is (S4). When the creation of the mail is completed, a signature sentence including control information is added to the mail (S5), and the mail is transmitted to the mail server 11 (S6).

  In this way, the function of automatically giving a signature text when creating an email is used, and control information is given to this signature text. Therefore, the signature text given the control information is automatically given to the email. Become. As a result, an operation error such as forgetting to give control information does not occur, and the trouble of manually giving control information for each transmission can be saved.

  FIG. 3 is a flowchart showing the processing contents of the control information confirmation unit 17 in the embodiment of the present invention. When the mail transmitted from the mail client 12 is input, the control information confirmation unit 17 performs a process of extracting control information from the mail (S1). It is determined whether or not control information has been extracted (S2). If control information can be extracted, a transmission determination process with control information is performed (S3). If control information cannot be extracted, a transmission determination process without control information is performed. Perform (S4).

  In the transmission determination process with control information in step S3, an inquiry is made as to whether the control information extracted from the mail exists in the control information database 16. Then, when there is a match, it is determined that transmission is possible, and when there is no match, it is determined that transmission is not possible. Details of this control information transmission determination process will be described later.

  In the transmission determination process without control information in step S4, it is determined that transmission is impossible in principle because there is no control information. Although control information does not exist exceptionally, it is determined that transmission is possible when a mail transmission destination is a specific destination (transmission destination mail address). This is because it can be determined that the address is reliable when the address is a specific address, and is not due to an unsolicited mail transmission by a virus. For example, when the destination is a predetermined destination such as in-house or a specific group, transmission is permitted as an exception even if there is no control information.

  Next, it is determined whether or not the determination results in steps S3 and S4 can be transmitted (S5). When it is determined that transmission is possible, the control information given to the mail is deleted (S6), and the mail is transmitted to the mail server 11 (S7). The reason why the control information attached to the mail is deleted when it is transmitted to the mail server 11 is to prevent a virus or the like from copying the control information of the mail. As a result, the control information is concealed to prevent unauthorized mail transmission.

  On the other hand, if it is determined in step S5 that transmission is impossible, mail transmission rejection processing is performed (S8). In the mail transmission rejection process, the mail is not transmitted to the mail server 11, but a mail having a content indicating that the transmission is rejected is notified to the transmission source address written in the main body of the mail. Details of the mail transmission rejection process will be described later. When the mail server 11 receives a mail from the control information confirmation unit 17, the mail server 11 performs a mail transmission process.

  In this way, by embedding the control information in the mail signature, only the mail intended by the sender is accepted and transmitted. Transmission of electronic mail by other programs such as viruses can be rejected because control information is missing.

  Next, a method for the mail client 12 to obtain control information will be described. As a method for the mail client 12 to obtain the control information, (1) notification by e-mail from the control information generation unit 15, (2) inquiry from the sender to the control information generation unit 15 using the mail client 12, (3 The mail client 12 obtains control information by either automatically obtaining the mail client 12.

(1) Notification by E-mail The control information generation unit 15 notifies each mail client 12 of information by e-mail. This is used regularly or when the control information is updated for some reason. The mail client 12 reflects the received control information in the signature text. Since it is notified by e-mail that the control information has been changed, it is possible to save the trouble of inquiring whether there is a change. In addition, since the signature text is automatically updated, omission of update can be eliminated.

(2) Inquiry to the control information generation unit 15 The sender makes an inquiry to the control information generation unit 15 using the mail client 12 to obtain control information. For example, when the sender accesses the Web server using the mail client 12, the Web server inquires the control information generation unit 15 about the control information. Alternatively, the control information is disclosed to the sender of the mail client 12 by referring to the control information database 16.

(3) Obtained automatically by the mail client 12 Generally, many commercially available mail clients 12 can call an external program such as a plug-in in order to realize an extended function. Using this function, the control information generation unit 15 is inquired for control information, and the result is reflected in the signature text. This saves the trouble of referring to the control information by the sender of the mail.

  Next, the control information creation timing in the control information generation unit 15 will be described. The timing at which the control information generation unit 15 creates the control information includes the following. First, control information is recreated periodically at regular intervals. Thereby, it is possible to prevent unauthorized mail transmission using old control information. Also, control information is recreated when instructed by the administrator. Furthermore, control information is recreated when the number of transmission rejection mails exceeds a threshold value within a certain period. When a terminal infected with a virus appears, control information is switched as a preventive measure.

  Next, giving control information to mail will be described. In the above description, the signature text is used as the location to which the control information is added. However, instead of the signature text, the control information may be added to a field in which mail can be input and transmitted. Further, a mechanism such as a template for a transmission mail may be prepared, control information may be assigned to the template, and control information may be automatically added to the created transmission mail. That is, the following are examples of places where control information is added to mail.

(1) Signature sentence When the place to which control information is added is a signature sentence, the automatic signature adding function of the mail client 12 can be used, and there is no omission of control information addition. The burden on the user can be reduced.

(2) Template for outgoing mail In the case of a mail client that uses a template for outgoing mail, a template can be used instead of a signature text. Thereby, the same effect as the case of a signature sentence can be acquired.

(3) Fields that can be entered by the sender Fields that can be entered by the sender include a subject (Subject) and a destination (To, Cc, Bcc). Give. In this case, the sender manually inputs each time an email is created.

(4) Mail header (unique field)
In the header of the mail to be sent, there is a mail client that can add a field in addition to a field that can be input by the sender. Control information is assigned to this field.

  Next, the transmission determination process with control information will be described. First, control information will be described. As described above, the control information itself uses, for example, a random character string that does not appear in the mail text or signature text. In other words, any character string that can be identified from a character string appearing in the body of an email or the like may be used. Further, by including various information in the control information, the transmission control method can be devised.

  For example, various information as shown below can be included. The information included in the control information mainly includes the expiration date of the control information itself, information on the outgoing mail, information obtained through communication with the mail client, and the like.

(1) Random number (2) Destination e-mail address (3) Source e-mail address (4) Importance specified for e-mail (5) Secret level specified for e-mail (confidential, confidential, etc.)
(6) Presence / absence of attached file (7) File name of attached file (8) Mail format (text, HTML, etc.)
(9) Electronic signature (10) Source address (IP address, telephone number, etc.)
(11) Mail client type and version (12) User name (13) Host name (14) Validity period

  The control information is basically created by the control information generation unit 15 as described above, but the control information generation unit 15 is also provided in the terminal 14 and is created by the control information generation unit 15 of the terminal 14. May be. In that case, a process of registering the control information generated by the control information generation unit 15 of the terminal 14 in the control database 17 is added.

Next, the transmission determination process with control information in the control information confirmation unit 17 will be described. The following three pieces of information are input to the control information confirmation unit 17.
(1) Control information given to mail (2) Mail itself (3) Information obtained by communication with mail client (address etc.)

It is determined from these three pieces of information whether mail can be transmitted. Examples of the determination method include the following. These may be determined alone or in combination.
(1) When control information exists in the control information database.
(2) When the transmission destination address of the mail matches or is included in the transmission destination mail address described in the control information.
(3) When the sender address of the email matches the sender email address described in the control information.
(4) When the importance level of the mail matches or is lower than the importance level described in the control information.
(5) When the secret level of the mail matches the secret level described in the control information, or lower.
(6) When the presence / absence of an attached file described in the control information matches the presence / absence of an email attachment.
(7) The case where the type of the attached file of the mail matches or is included in the type of the attached file described in the control information.
(8) The mail format described in the control information matches the mail format.
(9) The electronic signature described in the control information is a normal electronic signature.
(10) When the sender address of the mail client matches or is included in the sender address described in the control information.
(11) When the mail client matches or is included in the type and version of the mail client described in the control information.
(12) When the user name or host name used for communication by the mail client matches or is included in the user name or host name described in the control information.
(13) A mail is transmitted within the effective period described in the control information.

  As described above, when various kinds of information are included in the control information, it is possible to prevent unauthorized mail transmission by checking the included information. Further, although it is determined that the mail can be transmitted and the transmission process is performed, when the mail transmission process itself with the mail client 12 fails, it is determined that the transmission is impossible.

Next, the mail transmission rejection process will be described. The processing contents of the mail transmission rejection include the following.
(1) No transmission is performed.
(2) Accumulate mail rejected and send it when permission is granted.
When the sender or the administrator gives permission to send, the stored mail can be sent to the mail server. As a result, transmission can be performed when the sender does not give control information due to an operation error or when the mail is sent from a legitimate program or the like but no control information is given. .
(3) Notify that when transmission is refused.

Examples of notifications when transmission is rejected include the following.
(A) Notifying that the transmission has been rejected to the transmission source address of the transmission mail.
(B) The cumulative number of transmission rejections is notified collectively for a predetermined period.
(C) When the cumulative number of transmission rejections exceeds a predetermined value, collectively notify.
(D) Notify when the number of transmission rejections exceeds the upper limit within a certain period.
For example, if a large amount of mail is sent by a virus program, the number of communication rejections will be large and the number of notifications will be large. Or when the cumulative number of transmission rejections exceeds a predetermined value. Further, when the number of transmission rejections exceeds the upper limit within a certain period, it is determined that it is necessary to take a countermeasure against a virus program as soon as possible.
(E) Notify by other means.
For example, in the case of an electronic mail system using a Web server, it is an effective means to display and notify that transmission has been refused on the display screen of the terminal 14 on which the mail client 12 operates.

  If an email is rejected, there is a possibility of an unauthorized email being sent by a virus program, so if an event of rejection occurs, a notification to that effect will be sent to the sender or administrator immediately. By doing so, it is possible to quickly detect signs and take countermeasures against virus infection in the e-mail system.

  In the above description, it is necessary to store the control information to be given to the mail in the terminal 14 in some form. For example, it is necessary to hold it in the form of a signature sentence or the like. Therefore, when a virus program or the like obtains the file and attaches the file to the outgoing mail, it becomes possible to send the mail, and the ability to send only the mail intended by the sender is impaired. It can be.

  Therefore, as a countermeasure, the security is further improved by giving information to the outgoing mail that the virus program cannot easily obtain. As information that cannot be easily obtained by a virus program, for example, authentication information such as the fingerprint of a mail sender, the shape of a hand vein, the shape of an iris, or the like is used. In this case, an authentication information acquisition device that acquires the sender's authentication information is connected to the terminal 14 on which the mail client 12 operates, and the authentication information acquired by the authentication information acquisition device is transmitted as control information to the control information generation unit 15 in advance. The information is registered in the control information database 16.

  When the mail client 12 operating on the terminal 14 creates a transmission mail or actually transmits the transmission mail to the mail server 11, the mail client 12 obtains the authentication information by the authentication information acquisition device and assigns this to the transmission mail as control information. . Since the authentication information is registered in the control information database 16 as control information in advance, the control information confirmation unit 17 stores the control information given to the mail transmitted from the mail client 12 and the control information database 1617. By comparing with the control information, it is possible to determine whether mail transmission is possible.

  In this way, authentication information that can be given only when the sender performs transmission is used as control information, and since this control information is not left in the terminal 14, the virus program cannot easily use the information. Can be.

  Also, if the type of control information (various types of information included in control information) and the location where the control information is given are fixed, the sender and the sender when the type and location of the grant are analyzed by a virus program However, it may be damaged that only the intended mail can be sent.

  Therefore, as a countermeasure, the type of control information and the location to which the control information is added can be changed to further improve safety. The timing of change between the type of control information and the location to which the control information is added may be explicitly instructed by the administrator even at regular intervals or when the appearance of a virus program is confirmed.

  The control information generation unit 15 changes the control information to be generated to a specified format and content when a certain period of time has come, or in support of the change by an administrator or the like. The control information confirmation unit 17 changes the position of the control information to be extracted based on the changed type of control information and the assigned position, and changes the algorithm for determining that transmission is possible. The sender obtains the changed control information, obtains the position to which the control information is added, and assigns the control information to the mail to be transmitted according to the instruction.

  According to the embodiment of the present invention, an automatic assignment function such as a signature sentence or a transmission mail template that is normally provided in a mail client is used, and control information about the mail is embedded in the part, and when creating a mail or sending a mail At this time, since it is determined whether or not mail transmission is possible based on the control information, the burden on the mail sender is small, and it is possible to easily determine whether or not the sender intends to transmit. Since the transmission of the mail not intended by the sender is rejected, unauthorized mail transmission due to a virus or the like is suppressed.

  In addition, since the mail refused to be transmitted is notified to the sender, the manager, etc., the sender, the manager, etc. can cope with the mail refused to be sent, and measures against viruses can be taken at an early stage. For example, if the sender forgets to give control information due to an operational error, etc., it can recognize transmission rejection due to an operational error and detect that a virus program has sent a large number of emails. Entry can be detected.

  In addition, since the control information is not fixed and can be changed, transmission of virus program mail is suppressed even when a virus or the like refers to mail that has been successfully transmitted in the past, to which control information has been added. be able to. Furthermore, by changing the type of control information and the location to which it is added, the accuracy of distinguishing it from outgoing mail such as a virus program can be increased. It is not easy to create an outgoing mail that can be transmitted by a virus program by using, for example, biometric authentication information as control information by the authentication information acquisition device, not information that is always present in the terminal 14 such as a signature sentence as control information. Can be.

The block diagram of the electronic mail system concerning embodiment of this invention. The flowchart of the electronic mail transmission process in embodiment of this invention. The flowchart which shows the processing content of the control information confirmation part in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Mail server, 12 ... Mail client, 13 ... Control information server, 14 ... Terminal, 15 ... Control information generation part, 16 ... Control information database, 17 ... Control information confirmation part

Claims (22)

A mail client that attaches control information related to mail to a signature text and sends the signature text to an outgoing mail when sending the mail, and manages the control information and mail based on the control information given to the mail An e-mail system comprising: a control information server that performs a process for determining whether or not transmission is possible; and a mail server that receives a mail that has been determined to be transmittable by the control information server and performs a mail transmission process. The control information server includes a control information generation unit that generates control information, a control information database that stores control information generated by the control information generation unit, and a control that is given to an email transmitted from the email client. The electronic mail system according to claim 1, further comprising a control information confirmation unit that confirms whether information is stored in the control information database. The control information server rejects transmission to the mail server for mail to which the control information is not attached, and sends mail to the mail server when control information is attached. The electronic mail system according to claim 1 or 2. 4. The electronic mail system according to claim 3, wherein when the control information server rejects the transmission of the mail, the control information server transmits a mail having contents indicating that the transmission is rejected to the mail address of the transmission source. 5. The e-mail system according to claim 4, wherein the control information server collectively transmits e-mails indicating that transmission is rejected at predetermined time intervals. 5. The electronic device according to claim 4, wherein the control information server collectively transmits e-mails indicating that transmission is rejected when a predetermined cumulative number of transmission rejection e-mails exceeds a predetermined value. Mail system. 4. The e-mail system according to claim 3, wherein the control information server notifies the administrator when the number of e-mails whose transmission is rejected exceeds an upper limit value within a predetermined period. 7. The control information server according to any one of claims 3 to 6, wherein the control information server asks a sender or an administrator to determine whether or not to send a mail that has been refused transmission, and sends a mail to the mail server when there is a transmission permission. The electronic mail system according to claim 1. 9. The electronic mail system according to claim 1, wherein the control information server transmits the mail to the mail server after deleting the control information given to the mail. The date and time information indicating the validity period is included in the control information, and the control information server performs mail transmission processing only when the control information is within the validity period of the control information. The electronic mail system according to claim 1. The control information server refers to information on a destination mail address included in an email and determines whether or not to use the control information included in the email for the mail transmission process. 11. The e-mail system according to any one of 1 to 10. The control information includes information related to a destination email address included in the email, and the control information server performs email transmission processing based on the destination email address information and the email destination email address contained in the control information. The e-mail system according to any one of claims 1 to 11, wherein whether or not it is possible is determined. The control information includes information related to a sender email address included in the email, and the control information server performs email transmission processing based on the sender email address information included in the control information and the email sender email address. The e-mail system according to any one of claims 1 to 12, wherein the e-mail system is determined. The control information includes information related to a mail transmission source address, and the control information server performs mail transmission processing based on the information of the transmission source address included in the control information and the address of the mail client that has transmitted the mail. The e-mail system according to any one of claims 1 to 13, wherein the e-mail system is determined. 2. The control information includes electronic signature information related to a transmission source, and the control information server determines whether or not mail transmission processing is possible by confirming the electronic signature information included in the control information. The e-mail system according to any one of 1 to 14. The electronic mail system according to claim 1, wherein the control information server periodically changes the content of the control information. 17. The electronic mail system according to claim 16, wherein the control information server notifies the mail client of the changed control information by mail. 18. The electronic mail system according to claim 17, wherein when the mail client receives the changed control information from the control information server, the mail client automatically gives the changed control information to the signature text of the mail. The mail client obtains effective control information from the control information server when a sender creates a mail or periodically, and automatically adds the control information to a signature text of the mail. The electronic mail system according to any one of claims 1 to 18. The mail client is characterized in that, instead of a signature text, a place to which control information is given is sent by adding control information to a template of a sent mail, a field that can be input by a sender, or a mail head. The electronic mail system according to any one of 1 to 19. An authentication information acquisition device that acquires authentication information of a sender is connected to a terminal on which the mail client operates, and the authentication information acquired by the authentication information acquisition device is transmitted as control information to the control information server; 2. The e-mail system according to claim 1, wherein the control information received is managed. 2. The electronic mail system according to claim 1, wherein the control information server is capable of changing a type of control information and a location to which the control information is added.

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