E-mail firewall with stored key encryption/decryption

• US 6,609,196 B1
• Filed: 11/03/1998
• Issued: 08/19/2003
• Est. Priority Date: 07/23/1998
• Status: Expired due to Term

• Current Assignee: Axway Incorporated (Axway Software SA)
• Original Assignee: Tumbleweed Communications Corporation (Axway Software SA)
• Inventors: Dickinson, III, Robert D., Krishnamurthy, Sathvik
• Primary Examiner(s): Barron, Gilberto
• Assistant Examiner(s): Callahan, Paul E.
• Application Number:
  US09/180,377
• Time in Patent Office: 1,750 Days
• Field of Search: 709/314, 709/232, 380/259, 705/50, 705/55, 713/150, 713/160, 713/151, 713/161, 713/153, 713/154, 713/164
• US Class Current: 713/154
• CPC Class Codes: H04L 2209/76 Proxy, i.e. using intermediary entity to perform cryptographic operations network architectures or network communication protocols using hop-by-hop encryption H04L63/0464
• CPC Class Codes: H04L 51/063 Content adaptation, e.g. replacement of unsuitable content
• CPC Class Codes: H04L 51/212 using filtering or selective blocking
• CPC Class Codes: H04L 51/224 providing notification on incoming messages, e.g. pushed notifications of received messages
• CPC Class Codes: H04L 63/0227 Filtering policies mail message filtering H04L51/212
• CPC Class Codes: H04L 63/0245 Filtering by information in the payload
• CPC Class Codes: H04L 63/0263 Rule management
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 63/0464 using hop-by-hop encryption, i.e. wherein an intermediate entity decrypts the information and re-encrypts it before forwarding it

Abstract

An e-mail firewall (105) applies policies to e-mail messages (204) between a first site and a plurality of second sites in accordance with a plurality of administrator selectable policies (216). The firewall comprises a simple mail transfer protocol (SMTP) relay (202) for causing the e-mail messages (204) to be transmitted between the first site and selected ones of the second sites. A plurality of policy managers (216) enforce administrator selectable policies. The policies, such as encryption and decryption policies, comprise at least a first source/destination policy (218), at least a first content policy (220) and at least a first virus policy (224). The policies are characterized by a plurality of administrator selectable criteria (310), a plurality of administrator selectable exceptions (312) to the criteria and a plurality of administrator selectable actions (314, 316, 322) associated with the criteria and exceptions. The policy managers comprise an access manager (218) for restricting transmission of e-mail messages (204) between the first site and the second sites in accordance with the source/destination policy (218). The policy managers (216) further comprise a content manager (220) for restricting transmission of e-mail messages (204) between the first site and the second sites in accordance with the content policy (220), and a virus manager (224) for restriction transmission of e-mail messages (204) between the first site and the second sites in accordance with the virus policy (224).

Claims

1. An e-mail control system for controlling e-mail messages transmitted from and received by a computing site, comprising:

a message encryptor for encrypting a first designated type of message transmitted from a user associated with said computing site in accordance with at least a first stored encryption key;

a message decryptor for decrypting a second designated type of message sent to a user associated with said computing site in accordance with at least a second stored encryption key; and

a filter for monitoring said messages, after decryption by said decryptor and before encryption by said encryptor, in accordance with changeable filter information, the filter comprising at least a content filter to enforce content control policies by reference to specific words in the message body, each of said messages including at least one recipient address, the e-mail control system transmitting a message to said at least one recipient address in response to a predetermined policy result of said filter.

2. An e-mail control system as set forth in claim 1 wherein each of said messages comprise destination information, identifying at least a first destination for said message, and wherein said filter further comprises a destination filter for restricting transit of said messages which contain information corresponding to changeable destination filter information.

3. An e-mail control system as set forth in claim 2 wherein each of said messages comprise source information, identifying at least a first source for said message, and wherein said filter further comprises a source filter for restricting transit of said messages which contain information corresponding to changeable source filter information.

4. An e-mail control system as set forth in claim 3 further comprising means, responsive to said filter, for causing redirection of messages which contain information corresponding to said changeable filter information to a destination which differs from at least said first destination of said message.

5. An e-mail control system as set forth in claim 4 further comprising means, responsive to said filter, for causing redirection of messages which contain information corresponding to said changeable filter information to a destination which corresponds to at least said first destination of said message.

6. An e-mail control system as set forth in claim 5 further comprising:

notification means, responsive to said means for causing redirection of messages, for causing generation of a notification e-mail message; and

redirection means for causing transmission of said notification e-mail message to a destination corresponding to changeable notification message destination information.

7. An e-mail control system as set forth in claim 6 wherein said notification message comprises a body portion and wherein said notification means further comprises means for causing generation of a message contained in said body portion.

8. An e-mail firewall for restricting transmission of e-mail messages between a first site and a plurality of second sites in accordance with a plurality of administrator selectable policies, said firewall comprising:

a simple mail transfer protocol (SMTP) relay for causing said e-mail messages to be transmitted between said first site and selected ones of said second sites; and

a plurality of policy managers, responsive to said SMTP relay, for enforcing administrator selectable policies, said policies comprising at least a first source/destination policy, at least a first content policy and at least a first virus policy, said policies characterized by a plurality of administrator selectable criteria, a plurality of administrator selectable exceptions to said criteria and exceptions, said policy managers comprising,

an access manager for restricting transmission of e-mail messages between said first site and said second sites in accordance with said source/destination policy;

a content manager for restricting transmission of e-mail messages between said first site and said second sites in accordance with said content policy; and

a virus manager for restriction transmission of e-mail messages between said first site and said second sites in accordance with said virus policy, each of said e-mail messages including at least one recipient address, the e-mail control system transmitting a message to said at least one recipient address in response to a predetermined policy result of a policy manager.

9. An e-mail firewall as set forth in claim 8 wherein said policy managers further comprise a format manager, responsive to said administrator selectable policies, for converting said e-mail messages from a first format to a second format.

10. An e-mail firewall as set forth in claim 8 wherein said e-mail messages are formatted into a plurality of fields comprising a source field, a destination field, subject field, and a message field and wherein said access manager is responsive to said source/destination policy specified for each of said fields of said e-mail messages.

11. An e-mail firewall as set forth in claim 10 wherein said e-mail messages are further characterized by a size field and wherein said access manager is responsive to said source/destination policy specified for said size field.

12. An e-mail firewall as set forth in claim 10 wherein said e-mail messages are further characterized by a date and time field and wherein said access manager is responsive to said source/destination policy specified for said date and time field.

13. An e-mail firewall as set forth in claim 8 wherein said virus manager is responsive to e-mail messages containing compressed information for detecting viruses contained in said compressed information.

14. An e-mail firewall as set forth in claim 10 wherein said content manager is responsive, in accordance with said content policy, to information contained in said subject field and in said message field.

15. An e-mail firewall as set forth in claim 14 wherein said e-mail message further comprises an attachment field and wherein said content manager is responsive, in accordance with said content policy, to an attachment designated in said attachment field.

16. A method for restricting receipt of e-mail messages, in accordance with a plurality of changeable policies, to a first site from a plurality of second sites, the method comprising the steps of:

intercepting a first e-mail message transmitted to a user associated with said first site from at least one user associated with one of said second sites;

determining if said message is encrypted and decrypting said message in accordance with a stored key, if said message is encrypted; and

filtering said message in accordance with at least one stored content policy, said messages including at least one internal site recipient address, the e-mail control system transmitting the message to said at least one internal site recipient address in response to a predetermined policy result of said filtering.

18. A method as set forth in claim 16, wherein said filtering of said message comprises ensuring that an executable attachment is digitally signed.

19. A method as set forth in claim 18, wherein said digital signature certificate is an X.509 certificate.

17. A method for restricting transmission of e-mail messages, in accordance with a plurality of changeable policies, from a first site to a plurality of second sites, the method comprising the steps of:

intercepting an e-mail message transmitted to at least one user associated with one of said second sites from a user associated with said first site;

filtering said e-mail message in accordance with a plurality of stored policies, including at least one content policy to enforce content control policies by reference to specific words in the message body;

responding to a first of said stored policies by encrypting said e-mail message in accordance with a stored key; and

transmitting said e-mail message to at least one user associated with one of said second sites.