139 TCP UDP NetBIOS Session Service Official
A bit more info about NetBIOS (again from Wiki):
NetBIOS /ˈnɛtbʌɪ.ɒs/ is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network. As strictly an API, NetBIOS is not a networking protocol.
Basically a service like any other. Can be used for both good and ill. A wise policy is to deny all traffic not specifically needed by your machine in your firewall (look up IPTables, as it is the most common Linux firwall), but not everyone has time for that.
I think that an exploit of that sort is unlikely on Linux, but it is of course possible. I will note, however, that nothing can attack a port that doesn't have a service/daemon listening on it
( a bit tired so forgive me if this post is confusing)