When you are connected to the Internet you are sending and receiving information in small packets that contain directions, data, commands, etc. In other words everything that refers to your connection.
Protoport Personal Firewall 1.5 blocks intruders into your PC via the Internet or other networks, examining each data packet sent to you from other PCs, and filtering them according to their specifications, also establishing a double protection through NDIS and TDI drivers (where all network traffic enters).
It is outstanding because it hardly consumes resources nor affects your Internet connection speed. It supports all popular protocols: ARP, IP, TCP, UDP, ICMP, IGMP, IPX and OSPF, and also has antihacker and antitrojan protection, and will create an IP address blacklist.