CommView is a program for monitoring network activity capable of capturing and analyzing packets on any Ethernet network. It gathers information about data flowing on a LAN and decodes the analyzed data.

With CommView you can see the list of network connections, vital IP statistics, and examine individual packets. Packets are decoded down to the lowest layer with full analysis of the most widespread protocols. Full access to raw data is also provided. Captured packets can be saved to log files for future analysis.

Great program, easy to use. I love this program because it has an easy to use interface, it doesn't use much CPU or Memory, and you can add an alias to IP Addresses you want to remember. This makes it simple to block unwanted connections to your computer.

Source: download.com