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SPAMD(8)                OpenBSD System Manager's Manual               SPAMD(8)

NAME
     spamd - spam deferral daemon

SYNOPSIS
     spamd [-45dgv] [-B maxblack] [-b address] [-c maxcon]
           [-G passtime:greyexp:whiteexp] [-n name] [-p port] [-r reply]
           [-s secs] [-w window]

DESCRIPTION
     spamd is a fake sendmail(8)-like daemon which rejects false mail.  If the
     pf(4) packet filter is configured to redirect port 25 (SMTP) to this dae-
     mon, it will attempt to waste the time and resources of the spam sender.

     The options are as follows:

     -4      Return error code 450 to the spammer (default).

     -5      Return error code 550 to the spammer.

     -B maxblack
             The maximum number of concurrent blacklisted connections to allow
             in greylisting mode.  This value may not be greater than maxcon
             (see below).  The default is maxcon - 100

     -b address
             Specify the local address to which spamd is to bind(2).  By de-
             fault spamd listens on all local addresses.

     -c maxcon
             The maximum number of concurrent connections to allow.  The de-
             fault is 800.

     -d      Debug mode.  spamd does not fork(2) into the background.

     -G passtime:greyexp:whiteexp
             Adjust the three time parameters for greylisting; see GREYLISTING
             below.

     -g      Greylisting mode; see GREYLISTING below.

     -n name
             The SMTP version banner that is reported upon initial connection.

     -p port
             Specify a different port number from the default port that spamd
             should listen for redirected SMTP connections on.  The default
             port is found by looking for the named service spamd using
             getservbyname(3).

     -r reply
             The SMTP error to return to the spammer, i.e. 450, 451, 550.
             This defaults to 450.

     -s secs
             Delay each character sent to the client by the specified amount
             of seconds.  Defaults to 1.

     -v      Enable verbose logging.  By default spamd logs connections, dis-
             connections and blacklist matches to syslogd(8) at LOG_INFO lev-
             el.  With verbose logging enabled, message detail including sub-
             ject and recipient information is logged at LOG_INFO, along with
             the message body and SMTP dialogue being logged at LOG_DEBUG lev-
             el.

     -w window
             Set the socket receive buffer to this many bytes, adjusting the
             window size.

     spamd is designed to be very efficient so that it does not slow down the
     receiving machine.  Spam is never accepted, but always rejected with ei-
     ther a 450 or 550 error message.  The normal way that spam has been dealt
     with in the past is to either accept and drop, or outright block.  When
     configured to use 450 responses, spamd takes neither of these actions: it
     rejects the mail back to the senders' queue.

     spamd is best started from rc(8) in conjunction with the spamd-setup(8)
     which processes a list of spammers' addresses, and applies appropriate
     pfctl(8) rdr rules.  spamd-setup(8) is run from cron(8).

REDIRECTING SMTP CONNECTIONS
     With pf(4), connections to port 25 (SMTP) can be redirected to another
     host or port, based on the source address of the sender.  The rdr rules
     used for this purpose are described in pf.conf(5).  The rules can be
     loaded into a table to simplify handling.

         table <spamd> persist
         rdr pass inet proto tcp from <spamd> to any \
             port smtp -> 127.0.0.1 port 8025

     Any addresses in table &lt;spamd&gt; are then redirected to spamd running on
     port 8025.  Addresses can be loaded into the table, like:

         # pfctl -q -t spamd -T replace -f /usr/local/share/spammers

     spamd-setup(8) can also be used to load addresses into the &lt;spamd&gt; table.
     spamd-setup(8) also has the added benefit of being able to remove ad-
     dresses from blacklists, and will connect to spamd over a localhost sock-
     et, giving spamd information about each source of blacklist addresses, as
     well as custom rejection messages for each blacklist source that can be
     used to let any real person whose mail is deferred by spamd know why
     their address has been listed from sending mail.  This is important as it
     allows legitimate mail senders to pressure spam sources into behaving
     properly so that they may be removed from the relevant blacklists.

CONFIGURATION CONNECTIONS
     spamd listens for configuration connections on the port identified by the
     named service spamd-cfg (see services(5)).  The configuration socket lis-
     tens only on the INADDR_LOOPBACK address.  Configuration of spamd is done
     by connecting to the configuration socket, and sending blacklist informa-
     tion, one blacklist per line.  Each blacklist consists of a name, a mes-
     sage to reject mail with, and addresses in CIDR format, all separated by
     semicolons (;):

           tag;"rejection message";aaa.bbb.ccc.ddd/mm;aaa.bbb.ccc.ddd/mm

     The rejection message must be inside double quotes.  A \" will produce a
     double quote in the output.  \n will produce a newline.  %A will expand
     to the connecting IP address in dotted quad format.  %% may be used to
     produce a single % in the output.  \\ will produce a single \.  spamd
     will reject mail by displaying all the messages from all blacklists in
     which a connecting address is matched.  spamd-setup(8) is normally used
     to configure this information.

GREYLISTING
     When run in greylisting mode, spamd will run in the normal mode for any
     addresses blacklisted by spamd-setup(8).  Connections from addresses not
     blacklisted by spamd-setup(8) will be considered for greylisting.  Such
     connections will not be stuttered at or delayed, and will receive the
     pleasantly innocuous temporary failure of:

         450 Temporary failure, please try again later.

     in the SMTP dialogue immediately after the recipient is specified.  spamd
     will use the db file in /var/db/spamd to track these non-blacklisted con-
     nections to spamd by connecting IP address, envelope-from, and envelope-
     to, or "tuple" for short.

     A previously unseen tuple is added to the /var/db/spamd database, record-
     ing the time an initial connection attempt was seen.  After passtime min-
     utes (by default 30) if spamd sees a retried attempt to deliver mail for
     the same tuple, spamd will whitelist the connecting address by adding it
     as a whitelist entry to /var/db/spamd.

     spamd regularly scans the /var/db/spamd database and configures all
     whitelist addresses as the spamd-white pf(4) table.  The spamd-white
     table must be used to allow connections to pass to the real MTA as in the
     following pf.conf(5) example:

         table <spamd> persist
         table <spamd-white> persist
         rdr pass inet proto tcp from <spamd> to any \
             port smtp -> 127.0.0.1 port 8025
         rdr pass inet proto tcp from !<spamd-white> to any port smtp \
             -> 127.0.0.1 port 8025

     With this configuration, spamd-setup(8) should be used to configure
     blacklists in spamd and add them to the spamd pf(4) table.  These connec-
     tions will be stuttered at by spamd.  All other connections not in the
     spamd-white table are redirected to spamd but will not be stuttered at.
     Such connections will be considered for greylisting and eventual
     whitelisting (by addition to the spamd-white table so they are not redi-
     rected) if they retry mail delivery.

     spamd removes tuple entries from the /var/db/spamd database if delivery
     has not been retried within greyexp hours (by default 4) from the initial
     time a connection is seen.  The default is 4 hours as this is the most
     common setting after which MTA's will give up attempting to retry deliv-
     ery of a message.

     spamd removes whitelist entries from the /var/db/spamd database if no
     mail delivery activity has been seen from the whitelisted address by
     spamlogd(8) within whiteexp hours (by default 864, or 36 days) from the
     initial time an address is whitelisted.  The default is 36 days to allow
     for the delivery of monthly mailing list digests without greylist delays
     every time.  spamlogd(8) should be used to update the whitelist entries
     in /var/db/spamd when connections are seen to pass to the real MTA on the
     smtp port.

LOGGING
     spamd sends log messages to syslogd(8) using facility daemon and, with
     increasing verbosity, level err, warn, info and debug.  The following
     syslog.conf(5) section can be used to log connection details to a dedi-
     cated file:

           !spamd
           daemon.err;daemon.warn;daemon.info      /var/log/spamd

FILES
     /etc/spamd.conf

SEE ALSO
     pf.conf(5), services(5), spamd.conf(5), syslog.conf(5), pfctl(8),
     spamd-setup(8), spamdb(8), spamlogd(8), syslogd(8)

HISTORY
     The spamd command appeared in OpenBSD 3.3.

BUGS
     spamd currently uses the user ``_spamd'' outside a chroot jail when run-
     ning in greylisting mode, and requires the greylisting database in
     /var/db/spamd to be owned by the ``_spamd'' user.  This is wrong and
     should change to a distinct user from the one used by the chrooted spamd
     process.

OpenBSD 3.6                    December 18, 2002                             4