Scan For Open Ports

Part of any security regiment is to make sure the only ports you have open to the world is ones you want open and for most home systems you shouldnt have any open to the world/internet.

Theres a very good scanner built into linux called nmap that will scan your system and display a report on any ports and if they are TCP and/or UDP.

Install NMap

sudo apt-get install nmap

Scan Your System For Open Ports

nmap -v -sT localhost

Do A SYN Port Scan

sudo nmap -v -sS localhost

Any ports that show up you can cross check what the typical usage on the ports and services listing

This scan does a local system scan, ideally you need to scan your system from another machine and change "localhost" to your computers ip address. If you dont have another machine to use to scan your system you can use several free online scanners:

http://www.whatsmyip.org/port-scanner/

https://www.grc.com/x/ne.dll?bh0bkyd2

http://mxtoolbox.com/PortScan.aspx