Is there a way to block invites say from people not on your friend\’s list?

Don\’t get me wrong - grouping is a good thing and I do enjoy it. But last night I kept getting this random invite over and over..

Every one to two minutes the same player would invite me to group. It did not matter what zone I was in. Whispers went unanswered. This went on for about an hour and 1/2 until I logged off. I\’d never heard of the player before.

Is this some ki...