Starting with Windows XP SP1 and Windows Server 2003, ICF examines and drops (blocks) unsolicited inbound unicast, multicast, and broadcast traffic.

NOTE: Unicast traffic is transmitted between a single sender and a single receiver on the network.                                     Broadcast traffic is transmitted to all devices on the network.                                     Multicast traffic is transmitted to all devices on the network that request it (listening).
NOTE: Windows XP Tablet PC Edition and Windows XP Media Center Edition include SP1.

If you want to permit this traffic through the firewall, you must manually open the appropriate ports.

NOTE: If you open a port, inbound unicast, broadcast, and multicast traffic on that port and protocol are permitted.

NOTE: See tip 5289 ยป What is the Windows XP Internet Connection Firewall?