Unsolicited message intercepting communications processor

• US 7,673,058 B1
• Filed: 01/20/2004
• Issued: 03/02/2010
• Est. Priority Date: 09/09/2002
• Status: Expired due to Fees

• Current Assignee: Engage Technology
• Original Assignee: Engage Technology
• Inventors: White, Richard Paul, Spivack, Ira Victor, Huang, Alan, Lu, Haw-minn
• Primary Examiner(s): Kang; Paul H
• Application Number:
  US10/761,894
• Time in Patent Office: 2,233 Days
• Field of Search: 709/225, 709/229, 709/245
• US Class Current: 709/229
• CPC Class Codes: H04L 51/212 using filtering or selective blocking
• CPC Class Codes: H04L 51/48 Message addressing, e.g. address format or anonymous messages, aliases

Abstract

The spam blocker monitors the SMTP/TCP/IP conversation between a sending message transfer agent MTA_—0 and a receiving message transfer agent MTA_—1; catches MTA_—0'"'"'s IP address IP_—0, MTA_—0'"'"'s declared domain D_—0, from-address A_—0; to-address A_—1, and the body of the message; and uses this source and content information to test for unsolicited messages. It interrupts the conversation when MTA_—0 sends a .\r\n end-of-message indicator and uses the various test results to decide if the message is suspected of being unsolicited. If the message is suspected of being unsolicited then it logs the rejected message and sends an error reply to MTA_—0 which forces MTA_—0 to send a QUIT command before the body of the message is transmitted; else it logs the allowed message and releases the intercepted RCPT command which allows the conversation between MTA_—0 and MTA_—1 to proceed.

Claims

1. A networked computer comprising an unsolicited message rejecting communications processor connected between message transfer agents

MTA_0 with an Internet address IP_0, a from-address A_0, a declared domain D_0, and a real domain DD_0, and

MTA_1 with an Internet address IP_1, a domain D_1, and a to-address A_1

comprising:

a) monitoring means for monitoring the communications between MTA_0 and MTA_1;

b) determining means for determining if the communications contains a message that is unsolicited;

c) intercepting means for intercepting a .\r\n end-of-message indicator reply from MTA_0, forcing MTA_0 to QUIT its connection with the unsolicited message rejecting communications processor by sending an error reply to MTA_0 if the message is determined to be unsolicited;

wherein the unsolicited message rejecting communications processor does not intercept communications between MTA_0 and MTA_1 before a .\r\n end-of-message indicator reply from MTA_0 is received by the unsolicited message rejecting communications processor.

2. The unsolicited message rejecting communications processor in claim 1, further includes an allow_address database and wherein the determining means determines if the message is not unsolicited by checking if the IP_0 is in the allow_address database.

3. The unsolicited message rejecting communications processor in claim 1, further includes a prevent_address database and wherein the determining means determines if the message is unsolicited by checking if IP_0 is in the prevent_address database.

4. The unsolicited message rejecting communications processor in claim 1, further includes access to an open relay database and wherein the determining means determines if the message is unsolicited by checking if IP_0 is in the open relay database.

5. The unsolicited message rejecting communications processor in claim 1, further includes access to a DNS (domain name server) database and wherein the determining means determines if the message is unsolicited by checking if IP_0 has a domain name entry DD_0 in the DNS database.

6. The unsolicited message rejecting communications processor in claim 1, further includes a bad_from database and wherein the determining means determines if the message is unsolicited by checking if the from-address A_0 is in the bad_from database.

7. The unsolicited message rejecting communications processor in claim 1, further includes a suspect_domain database and wherein the determining means determines if the message is unsolicited by checking if the real domain DD_0 matches the domain of the from-address A_0 and the domain of the from-address A_0 is in the suspect_domain database.

8. The unsolicited message rejecting communications processor in claim 1, wherein the determining means determines if the message is unsolicited by checking if the from-address A_0 matches the to-address A_1.

9. The unsolicited message rejecting communications processor in claim 1, further includes a no_filter database and wherein the determining means determines if the message is to be rejected if it is determined to be unsolicited.

10. The unsolicited message rejecting communications processor in claim 1, wherein the determining means determines if the message is unsolicited by checking if the declared domain D_0 is the same as the domain D_1.

11. The unsolicited message rejecting communications processor in claim 1, wherein the determining means determines if the message is unsolicited by checking if the declared domain D_0 does not match the real domain DD_0 and the declared domain D_0 is in the suspect_domain database.

12. The unsolicited message rejecting communications processor in claim 1, further includes a bad_word database and wherein the determining means determines if the message is unsolicited by checking if the subject line of the message contains any words in the bad_word database.

13. The unsolicited message rejecting communications processor in claim 1, further includes a bad_fingerprint database and wherein the determining means determines if the hash “

fingerprint”

of a portion of the body of the message is in the bad_fingerprint database.

14. The unsolicited message rejecting communications processor in claim 1, further includes a rejected_connection database which logs the time, from-address A_0, to-address A_1, and the reason for the rejection if the message is determined to be unsolicited.

15. The unsolicited message rejecting communications processor in claim 1, further includes an allowed_connection database which logs the time and to-address A_1 if the message is determined not to be unsolicited.

16. A method for

a receiving networked computer with an Internet connection, a message transfer agent MTA_1, an Internet address IP_1, a to-address A_1, and an operating system capable of executing the method

to reject unsolicited messages from

a transmitting networked computer system with an Internet connection and a message transfer agent MTA_0, an Internet address IP_0, a from-address A_0, a declared domain D_0, and a real domain DD_0

comprising the steps of:

a) waiting for a new SMTP connection request;

b) relaying and monitoring the replies from MTA_0 to MTA_1;

c) relaying replies from MTA_1 to MTA_0;

d) intercepting the .\r\n end-of-message indicator reply from MTA_0 to MTA_1;

e) determining if the message is unsolicited by analyzing the monitored replies;

f) releasing the intercepted .\r\n end-of-message reply if the message is determined not to be unsolicited; and

g) sending an error reply to MTA_0 to force MTA_0 and MTA_1 to close down their connection;

whereby MTA_1 controls the interaction between MTA_0 and MTA_1 until a .\r\n end-of-message indicator reply is received from MTA_0.

17. A method for

a receiving networked computer with an Internet connection, a DNS server, and an open relay database, a message transfer agent MTA_1, an IP address IP_1, a domain name D_1, a to-address A_1, an allow_address database, a prevent_address database, a suspect_domain database, a bad_from database, a no_filter database, a yes_filter database, a bad_word database, a bad_fingerprint, a rejected_connection database, an allowed_connection database, and an operating system capable of executing the method

to reject unsolicited messages from

a transmitting networked computer system with an Internet connection, a message transfer agent MTA_0, an IP address IP_0, a declared domain D_0, a real domain DD_0, and a from-address A_0

comprising the steps of:

a) waiting for a SMTP connection request on the receiving networked computer system'"'"'s Internet connection;

b) sending a 220 reply to MTA_0 to acknowledge the SMTP connection request;

c) extracting the IP address IP_0 from the SMTP connection request;

d) requesting the domain name DD_0 for IP_0 from the DNS server;

e) testing if the domain name DD_0 is “

no name”

;

f) testing if IP_0 is in the open relay database;

g) testing if IP_0 is in the allow_address database;

h) testing if IP_0 is in the prevent_address database;

i) requesting a connection with MTA_1;

j) waiting for a 220 reply from MTA_1 to acknowledge the requested connection;

k) waiting for a reply from either MTA_0 or MTA_1;

l) jumping to step o) if the reply is not from MTA_1;

m) relaying the reply from MTA_1 to MTA_0;

n) jumping to step k) to wait for a new reply;

o) jumping to step u) if the reply from MTA_0 is not a HELO;

p) extracting the declared domain D_0 from the reply;

q) testing if the declared domain D_0 matches the domain D_1;

r) testing if the declared domain D_0 does not match the real domain DD_0 AND the declared domain D_0 is in the suspect_domain database;

s) relaying the HELO reply from MTA_0 to MTA_1;

t) jumping to step k) to wait for a new reply;

u) jumping to step aa) if reply from MTA_0 is not a MAIL;

v) extracting the from-address A_0;

w) testing if A_0 is in the bad_from database;

x) testing if DD_0 does not match the domain of A_0 and the domain of A_0 is in the suspect_domain database;

y) relaying MAIL reply to MTA_1;

z) jumping to step k) to wait for a new reply;

aa) jumping to step ii) if the reply from MTA_0 is not a RCPT;

bb) extracting the to-address A_1;

cc) testing if A_1 is in the no_filter database;

dd) testing if A_0 matches A_1;

ee) testing if A_0 is in the no_filter database;

ff) testing if A_0 is in the yes_filter database;

gg) relaying RCPT reply to MTA_1;

hh) jumping to step k) to wait for a new reply;

ii) jumping to step yy) if the reply from MTA_0 is not DATA;

jj) relaying DATA to MTA_1;

kk) waiting for a 354 reply from MTA_1;

ll) relaying the 354 reply to MTA_0;

mm) wait for the body of the message;

nn) relaying the body of the message to MTA_1;

oo) waiting for a .\r\n end-of-message indicator;

pp) testing if any word in the subject line of the message is in the bad_word database;

qq) testing if the hash “

fingerprint”

of a portion of the message is in the bad_fingerprint database;

rr) jumping to step vv) if NOT (t_allow OR t_no_filter OR OR NOT t_yes_filter OR NOT (t_prevent OR t_open OR t_DD-) OR t_bad_from OR t_suspect_domain OR t_echo_domain OR t_forged_domain OR t_bad_word OR t_bad_fingerpring));

ss) logging the time and the to-address A_1 in the allowed_connection database;

tt) relaying the .\r\n end-of-message indicator reply to MTA_1 to continue the conversation;

uu) jumping to step k) to wait for a new reply;

vv) logging the time, the from-address A_0, the to-address A_1, and the reason for rejecting the connection in the rejected_connection database;

ww) sending a 554 reply to MTA_0 to terminate the conversation;

xx) jumping to step k) to wait for a new reply;

yy) jumping to step ggg) if the reply from MTA_0 is not RSET, SEND, SOML, SAML, VRFY, NOOP, EXPN, HELP, or TURN;

zz) relaying the reply to MTA_1;

aaa) jumping to step j) to wait for a new reply;

bbb) jumping to step ddd) if the reply from MTA_0 is not a QUIT;

ccc) relaying the QUIT reply to MTA_1;

ddd) waiting for a 221 reply from MTA_1

eee) relaying the 221 reply from MTA_1 to MTA_0;

fff) jumping to step a) to wait for a new connection;

ggg) sending a 500 reply to MTA_0 to signal a syntax error; and

hhh) jumping to step a) to wait for a new connection.

18. A method in a networked computer comprising an unsolicited message rejecting communications processor connected between message transfer agents MTA_0 and MTA_1, said method comprising:

monitoring communications between MTA_0 and MTA_1;

determining if the communications contains a message that is unsolicited; and

intercepting a .\r\n end-of-message indicator reply from MTA_0, forcing MTA_0 to QUIT its connection with the unsolicited message rejecting communications processor by

sending an error reply to MTA_0 if the message is determined to be unsolicited;

wherein the unsolicited message rejecting communications processor does not intercept communications between MTA_0 and MTA_1 before a .\r\n end-of-message indicator reply from MTA_0 is received by the unsolicited message rejecting communications processor.