Start with a whois on the IP address. See where the connection is. Then open a web browser, go to the IP, and see if there is a site hosted there. Of course, the IPs that they are coming from, are probably not IPs sites are hosted on, but at least you can see the location in which the IP is coming from, then in the whois of your competitor's sites, you can see if the registration addresses match the location of the IP. Just a few things.