Strangely, spam was not a problem on the lists that I used to work on full-time and managed lists here and elsewhere.  That's not to say that no subscriber's email never got infected, nor that some infected machine didn't spoof a subscriber.

Depending upon the list, various parameterizations and procedures were followed that really did seem to minimize list-distributed spam.

SUBSCRIPTION= OPEN,CONFIRM

NOTIFY= YES

SEND= PRIVATE
or
SEND= PRIVATE,CONFIRM

DEFAULT-OPTIONS= REVIEW (until subscriber was vetted in some way)

SIZELIM= 250

ATTACHMENTS= NO
or
ATTACHMENTS= NO,FILTER

DAILY-THRESHOLD= nn

OWNERS= [more than one individual]


file listname.MAILTPL

>>> CONTENT_FILTER OOO and blank Subject
Subject: Out of office
Action: MODERATE OOO messages are not allowed on this list.
Subject: Out of the office
Action: MODERATE OOO messages are not allowed on this list.
Subject::
Action: MODERATE Please resubmit with a non-blank subject.
Text: Out of office
Action: MODERATE OOO messages are not allowed on this list.
Text: Out of the office
Action: MODERATE OOO messages are not allowed on this list. 



Foolproof?  No
More Hands-on? YES
Customer Satisfaction? High