groups joining my session????

What the hell is going on here??? The last 2 times ive gone online right the begining it says a name of some group that has joined my session??? I did not allow ANYONE 2 join my session!!! How does this happen??? One time recently it said that amazon had joined my session??? How R they doing this and Y??? Does anybody know the answer? I have the premium version of Avast?

Some more details might help, what session/groups, etc.

A screenshot of the Avast alert might help, attach it to your next post.