qmail/spp/ra-plugins/tarpit

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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.

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MoinQ: qmail/spp/ra-plugins/tarpit (last edited 2022-03-28 01:45:15 by ToshinoriMaeno)