you can block network access through wireless need to do this step the Right click on that - click 'view available wireless networks you should see your own network - if it has a padlock, it is security enabled making it more difficult for your neighbors to log on for further assistance visit http://www.iyogi.co.uk
when you use the internet from the wireless you want to secure the wireless connection.
you will found an wireless icon on the system tray of the computer or the laptop.
right click on the wireless icon and select view available networks.
you will see the list of the networks . select your own network and see is your network should be padlock.
if it is padlock than your network is secure and no one can not access.