Norton Firewall Activity Log Help

I've been receiving many port intrusion notices over the past few months (since  January) and I am trying to make sense of them and figure out what is going on. I keep getting entries  like the following in the  log:

 

Attempted Intrusion "Portscan" against your machine was detected and blocked.
Intruder: 61.139.105.163(12200).
Risk Level: Medium.
Protocol: TCP.

I have received over thirty of these messages over the last several months and almost all of them are coming from the same IP address. I tried to look up the IP on a website and it says that it is coming from China. I don't know anyone from China so I really have no  idea what is going on here. Can someone  help me make sense of this? I'm worried and wondering what I  should do about this to protect my computer. Any advice  would be very much appreciated.

 

Thank you