We had similar scary numbers when McAfee was tracking them! A lot of people have spare time on their hands, so they install programs that 'ping' IP addresses of computers (the number given to your computer when you're connected to the internet) to see which ones might be insecure (so they can hack inside them or do other devious things). Someone else might have another explanation.

We uninstalled McAfee as it was slowing down the computer too much and driving us nuts to download updates almost daily. We have PC-Cillin now and it's a bit better (though not much). That's the price of security I guess