spam or worse coming through list

[Guest guest]

It seems as though the moderator(s?) have a good handle on this group.  However, every so often, perhaps weekly, a message will come through the group with images or other spam.  I don't open them, of course, but can read the first line through my gmail.  Is everyone else getting these.  At first I just set up a filter so that messages from those sender would be diverted to spam straight away.  But, then new ones appear from 'new' sender names.

Thanks for any help with this,Melani