getting attacked on computer

what does window messenger has to do with it? are you talking about like the msn one? the one with the green person icon? but i think i use a hub it has lots of plugs to put the ends of your like 4 network cables and then for the cable modem plug and then the power, thats a hub right? what do i do? but my brother has the same thing and he never gets attacked?? we use the hub to share a internet connection