Its customisable in the who's online section in the vbulletin options section in the admincp of vbulletin.
Sweet, cheers for that! Vbulletin has so many options and settings I don't even know whats under my nose!
That's why I picked Vbulletin over some lame phpbb. I dis-like phpbb. I love powerful backends and so I decided "Well Vbulletin it is"