ASPEWS is a list of areas on the Internet which several system administrators, ISP postmasters, and other service providers have assembled and use to deny email and in some cases, all network traffic from.

This list has been provided to replace the seemingly defunct Spam Prevention Early Warning System (SPEWS) list. This list is not connected or related to the Anonymous Postmasters Early Warning System (APEWS) list.

Most spam advisory and blocking systems work after the fact. There is a time lag between the spammer setting up shop, spamming millions, and getting netblocks listed by these systems. ASPEWS identifies known spammers and spam operations, listing them as soon as they start, sometimes even before they start spamming.

ASPEWS also found that several of the several popular spam advisory and blocking systems have become bogged down due to an overload of requests. This lessens their effectiveness. ASPEWS does not run a request or nomination based list. Entries in the list come from the knowledge and experience of the people who set up and use the ASPEWS lists.

Any mailservers using the ASPEWS list to filter can be configured to do several things with incoming mail from ASPEWS listed IP addresses. The recommended method is to reject the message with a link to the ASPEWS “Why was I referred to this website?” page.