To find out an open port, you will need to carry out a port scan. Open the Command Prompt from ‘Start | Run | cmd.exe’ and enter the command netstat -ano and hit ‘Enter’ (e.g. C:\Documents and Settings\Administrator>netstat –ano).This will list all currently active network connections.
To know if any port is open for data transferring, look the note under ‘State’. For example, see under ‘Foreign address’ (Remote address) column. If the value of the field is ‘0.0.0.0:0’ then no one can send data through these ports. If you find an IP address instead, you need to verify the program with the help of the displayed process ID (numbers shown under PID).
The best tool for finding this is Process Explorer from Microsoft (latest version 11.32). Download and run this program (you can use Windows own process explorer by entering Ctrl+Alt+Dele or Ctrl+Shift+Esc). Now verify the program by looking under PID. For example, if you find an open connection with the 764 PID, you need to find the same number in the Process Explorer.
To block any data transfer through the open port you need to block that port using your firewall. For example, if the IP address in an open port is 127.0.0.1:1026, you must block the 1026 port.