|Source Network Address: --random ip --|
How random are the IPs? Do you see any repeats? Have you done a whois on any of them & contacted the administrator? Is your server in the DMZ with a public IP or is it behind a router.
I would have the server behind a router with an internal IP address & just forward the ports that are necessary to allow remote access if needed. If it's a web server, you might want to host it separately from your network.
How do you know when a politician is lying? His mouth is moving.