NAME tarpit DESCRIPTION This plugin lets you do tarpitting on your SMTP server. Tarpitting is a mechanism to slow down the incoming mail from prolific senders, by inserting progressively larger delays after every RCPT. Sadly, the effectiveness of tarpitting has decreased, as spammers adapted by using multiple connections instead. Check the ipthrottle(8) plugin for a way to control that. Anyway, it's probably a good idea to enable tarpitting. At least it should do no harm. This plugin should be used only on the RCPT command. REQUIREMENTS None. It may cause latency on sending mail, but that is the goal of the plugin ;-) CONFIGURATION You can set the TARPITCOUNT environment variable to set at which RCPT the tarpitting starts. It defaults to 50. The TARPITDELAY environment variable can be set to a number, or the letters N (Normal), M (Medium) or H (Hard) and affects the way the delay increases. It defaults to 2. Number Delay each tarpitted recipient by this number of seconds. Normal Delay each tarpitted recipient 2 seconds more than the previous one. Medium Delay each tarpitted recipient 5 seconds more than the previous one. Hard Delay is the square of the number of tarpitted recipients. So, passing the TARPITCOUNT, they delay like this: TARPITDELAY=2 2,2,2,2,2 TARPITDELAY=N 2,4,6,8,10 TARPITDELAY=M 5,10,15,20,25 TARPITDELAY=H 1,4,9,16,25,36,49 Obviously, setting TARPITDELAY to 0 disables tarpitting. LOGGING When the user crosses the tarpitting threshold, it will log: tarpit: pid 5432 - Started tarpitting. ERROR MESSAGES Should never produce error messages. SEE ALSO plugins-ra(8), ipthrottle(8) Homepage: http://ralsina.blogsite.org/stories/39.html COPYRIGHT Copyright © 2006 Roberto Alsina Copyright (C) 2004 Pawel Foremski For any questions please contact Roberto Alsina, because this version is heavily modified from Mr. Foremski's original. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.