ATHG is an unmoderated listserv, so what arrives gets sent (unless the
listserv manager detects that it is SPAM, i.e., commercial email sent to a
vast number of people offering scams on how to get rich quick,
etc.).  Although I have a program that automatically updates my anti-virus
software monthly, I open attachments from only people whom I know and urge
everybody else to do the same.  My main problem comes from students who
send papers from computer labs, notoriously virus-ridden places.  I confess
that I don't know how anti-virus software works; I do know that I
occasionally get email with the picture of a bug next to it and
instructions to delete without reading.