BLD stands for "blacklist daemon" and is intended
to serve a blacklist. The blacklist is built by
simply inserting IP addresses or by using
submission rate limits based on a maximum number
of submissions of the same IP address within a
minimum time interval. A BLD cluster can be built
by configuring the daemon to notify other similar
daemon(s) every time an IP address is added to the
blacklist. BLD was primarily designed to fight
against dictionary-based spam (by making the MTA
report to BLD any host that tries to send email to
an unknown user), but can be used by any program.
