Quoting John F. Woods,

> According to my modem lights and netstat -picmp, someone out there in IP land
> seems to be constantly pinging my system (not a flood ping, thank goodness).
> Is there an existing program that can be used to figure out the source of these
> packets?  I assume I can knock something together using BPF, but I am hoping
> that someone here has already solved this problem...

I'm sure that tcpdump is willing to help you out? I.e. something like:
tcpdump -i <your_interface> ip proto icmp

- Frank