Backscatter

PROBLEM: Mailman comes out of the box ready to backscatter spam people.

RESOLUTION:

1. Don't create backscatter aliases for subscribe/unsubscribe/etc by default. Nearly everyone uses web based signup.
2. Discard or hold messages from non-subscribers by default.

DETAILS:

Removing aliases depends on the installation method.

• If using mm-handler, an experimental version is available that can optionally remove support for the problem aliases at http://home.uchicago.edu/~dgc/sw/mailman/mm-handler/mm-handler-2.10.

Discard or hold messages from non-subscribers by default

The normal default setting for new lists is to hold messages from non-members. If appropriate, you can change this default to discard by putting

DEFAULT_GENERIC_NONMEMBER_ACTION = 3

in mm_cfg.py, and of course, you can change generic_nonmember_action for any specific list after it is created.

Also, if generic_nonmember_action for a list is hold, you can consider setting the list's respond_to_post_requests to No. There is no configuration setting to make this No by default for new lists. Note however that the number of such autoresponses to a single address is limited to MAX_AUTORESPONSES_PER_DAY which defaults to 10, but can be set as low as 1 in mm_cfg.py.

For an existing list, generic_nonmember_action may be changed through the web administrative interface or using the config_list utility. This setting may be found in the web interface for a list under Privacy Options, Sender Filters. To set this value from the command line for every list:

cd /path/to/mailman/bin
f=`mktemp`
echo generic_nonmember_action = 3 > $f
for list in `./list_lists --bare`
do ./config_list -i $f $list
done
rm $f