Most people secures their network, but not always it is the right security.
When you set up your wireless network, always remember to use strong password.
Also never forget to change your admin panel password, since this can be found on the internet. Just by knowing the brand you use.
It is very easy to change from low security to high security password. Use numbers, capital letters and normal letters, a good mix is always best. And please have more than 8 characters!