Every release of the viewer and server software has more fixes to stop griefing. But it is an escalating problem. Sort of an arms race.
A recent casualty appears to be the Pornstars group. It seems that group is going to close because of griefer infiltration. It will be replaced with a new group: The Sexiest® : Pornstars click the name to find the group.
You may be unexpectedly ejected from the group. That will be the group closing. There is some hope this may be avoided. But, that depends on whether the Lab helps out.
Many are hoping the coming Group Ban Lists will help with this problem.