My router logs are filled with entries that indicate my Xubuntu box suddenly, as of a couple of days ago, is pinging seemingly random, changing IP addresses every 10 seconds or so.

I've run a sudo netstat -catupe for several minutes, then searched it looking for the ip addresses pings were sent to according to the router logs, and haven't found a match.

What could be doing this sudden pinging, and what I am doing wrong to figure out what is doing it?

Thanks for any assistance you can provide!