"unknown service" port 3369 usr/bin/grep

 

I am getting the pop up in Norton Firewall, as an alert that says: "An unknown service is starting on your Mac. If you don't change firewall setting, the firewall will block connections from other computers to this service on your Mac." More Information: Application usr bin grep. Port 3369 (unknown service). 

I just need to know what this is and if I should allow it.

Thanks for any help you can give me on this.