초록 ▼

An Active Filtering proxy filters electronic junk mail (also known as spam, bulk mail, or advertising) received at a Message Transfer Agent from remote Internet hosts using the Simple Mail Transfer Protocol (SMTP). The proxy actively probes remote hosts that attempt to send mail to the protected mai

An Active Filtering proxy filters electronic junk mail (also known as spam, bulk mail, or advertising) received at a Message Transfer Agent from remote Internet hosts using the Simple Mail Transfer Protocol (SMTP). The proxy actively probes remote hosts that attempt to send mail to the protected mail server in order to identify dialup PCs, open relays, and forged email. The system provides multiple layers of defense including: connect-time filtering based on IP address, identification of dialup PCs attempting to send mail, testing for permissive (open) relays, testing for validity of the sender's address, and message header filtering. A sender's message must successfully pass through all relevant layers, or it is rejected and logged. Subsequent filters feed IP addresses back to the IP filtering mechanism, so subsequent mail from the same host can be easily blocked.

대표청구항 ▼

[ I claim:] [1.]1. A system for detecting and selectively preventing reception of an electronic message to a local message transfer agent (MTA), the electronic message having an address identifying a sender and transferred over a connection from a remote host, the system comprising:a dialup filter d

[ I claim:] [1.]1. A system for detecting and selectively preventing reception of an electronic message to a local message transfer agent (MTA), the electronic message having an address identifying a sender and transferred over a connection from a remote host, the system comprising:a dialup filter determining whether the connection is a dialup connection and, if the connection is a dialup connection, terminating the connection;a relay filter determining whether the remote host is an open relay and, if the remote host is an open relay, terminating the connection; and,a user filter verifying whether the sender of the electronic message is authorized and, if the sender of the electronic message is not authorized, terminating the connection;wherein, said system establishes communication over the connection between said remote host and the local MTA if said system determines that the connection is not a dialup connection, said relay filter determines that the remote host is not an open relay and said user filter verifies the sender as authorized.