bart = Bootable Anti-virus Recovery Tools as stated in the mouseover in the posting from Tarq57
the avast is up to date when you update it at the moment you write it
you can repeat this proces a lot of times everytime costing you a cd or if your smart a rewritable cd
BART also has some network drivers in it, surely it doesnt support all the cards so u have to be lucky for that, but if it does have support then you can
let bart update it self at that moment for that session via internet connection
but when you get infected by a new virus you always download the most recent definitions right..... so same goes for bart cd except you have to bake the cd after it
and i believe that bart runs of the WINPE enviroment, not linux.... (any avast tech here can confirm this?)