Networks

1.Can someone break in to your wireless network

Yes depending on the locality and building material of the house anyone within a 500 metres radius could break into the WiFi in your house.

2. can they take your files

Yes they can but more importantly they can download material that you are held responsible for. Things like Kiddy Porn or Terrorist Material can be downloaded through your WiFi Connection and the authorities will consider the owner of that ISP Connection responsible for the download.

3. can they control your computer

Depends on what OS you are using and how secure it is. But if you are talking any Windows System then the answer is most defiantly yes.

4 how long would it take then to hack the secure code.

If you mean WPA2 under 10 seconds if the person involved knew what it is that they are doing. If they do not know it will take longer. If you do not run WPA2 it can take considerably less time and if you have not changed the Password on the WiFi Access Point anyone could enter it's URL and be in within a few seconds.

Col

I think when I get home I am going to do this as well. But you can set your router up to only allow specific MAC addresses to connect.

All of the above. There are things you can do to make the infiltrators access harder to achieve their goals. One is the MAC address filtering but even that isn't that secure as the address can be spoofed. One way to limit outside access is to insure none of your WIFI signal leaves the premises. Working with a laptop outside the home could identify signal levels and changing position of the router and its antenna(s) can create usable signals within the home but not outside. Some signal peaking areas can be reduced with grounded foils to block signals in certain directions but this can also inscrease the signal in others and is all variable depending on the environment, wall insulation, wiring and innumerable other variables.

if your brother has "wires running all over his house", but has a wireless-capable router and not disabled the wireless connectivity in it, then he is vulnerable as several posters have noted.

we at Techrepublic do not encourage or respond with info on how to hack systems.

It seems like a line is being crossed here (or at least fast approaching.)