It can be a security risk to have unwarranted open ports.
So I ran
nmap 192.168.0.1 to investigate if I had open ports on my home network, it turns out, I do:
PORT STATE SERVICE 53/tcp open domain 80/tcp open http 5431/tcp open park-agent 49163/tcp open unknown
This concerned me. However, upon further reading, I have discovered that running
nmap from my home desktop does not obtain the actual open ports, but rather ports which are accessible from my desktop on the local network side; I'm interested in ports open to the Internet at large.
Therefore, I tethered my desktop to my phone Wi-Fi Hotspot and ran
nmap again, this time I am outside of my local network, i.e. I am not connected to my home router provided by my ISP but rather connected to the Internet through my phone service provider. I ran
nmap again, this time using the external
IP Address of my home network. The output is as follows:
PORT STATE SERVICE 21/tcp open ftp 80/tcp open http 113/tcp closed ident 443/tcp open https 1935/tcp open rtmp 8080/tcp open http-proxy
There are still numerous open ports, which I was not expecting, as I am not running any servers and simply use my home network for Internet browsing.
Given the answers here, I do not think I should have any open ports.
Why are these ports open to begin with? And should I be concerned/close them?
Edit: I have a single gateway device provided to me by my ISP. I have one desktop connected to this device. My ISP is Sky.