If you have any kind of intrusion detection set up like Psionic’s PortSentry or a personal firewall, you’ll see attempts to connect on ports you may not be familiar with. Even looking up the port in /etc/services doesn’t tell the whole story. To find all known network services, trojans, worms and exploits associated with a given port, go to Internet Storm Center’s Port Reports. And since you’re in sleuth mode, why not go to samspade.org and see what you can find out about the IP address the scan originated from.