Someone

  x NetBIOS name service requests are sent as broadcast messages from an                                                                            x  
  x unprivileged port and responded to with unicast messages to the                                                                                 x  
  x same port. This make them hard to firewall properly because connection                                                                          x  
  x tracking doesn't deal with broadcasts. This helper tracks locally                                                                               x  
  x originating NetBIOS name service requests and the corresponding                                                                                 x
  x responses. It relies on correct IP address configuration, specifically                                                                          x  
  x netmask and broadcast address. When properly configured, the output                                                                             x  
  x of "ip address show" should look similar to this:                                                                                               x  
  x                                                                                                                                                 x  
  x $ ip -4 address show eth0                                                                                                                       x  
  x 4: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000                                                                           x  
  x     inet 172.16.2.252/24 brd 172.16.2.255 scope global eth0