Your computer behaves weirdly. in a way that you haven’t seen before.
You hear sudden sounds, played at accidental
Programs start unpredictably
Your personal firewall tells you that an application has tried to connect to the Internet.
Your computer ‘freezes’ frequently, or programs start running slowly.
You get lots of system error messages.
The operating system will not load when you start your computer.
You notice that files or folders have been deleted or changed.
You notice hard disk access when you’re not aware of any programs running.

Why is it essential to secure my wireless network?
These days, most computers are wireless-enabled: they let you connect to the Internet without a physical network cable. The major benefit, of course, is that you can use your computer anywhere in the house or office there are potential risks involved in wireless networking - unless you make your network secure:

A hacker could interrupt any data you send and receive;
A hacker could get access to your wireless network;
Another person could hijack your Internet access.
Therefore, if your wireless network is not protected, a hacker could intercept any data you send; access your network, and therefore your shared files; use your bond to connect to the Internet - especially significant if you have a download limit on your internet package and your bandwidth is being swallow up by a captor