Hello,
(ANS) No.1 YES! sadly, other people 100% will hijack your bandwidth if you allow them too (give them half a chance). NOT securing your wireless router can be likened to leaving the keys to your house in the front door lock with the door flapping wide open in the breeze. If you went out leaving the door to your house in this condition then you would be very naive if your house got burgled on your return. i.e. came home only to find someone had riffled through your personal possessions. NOT securing your wireless router is no different.
No.2 How to enable security.
To secure your router you first of all need to connect to the routers administrative pages (set up pages or configuration pages). Use the Ethernet patch cable & any available laptop or desktop that has a network card. Most routers use a default kind of IP address such as 192.168.1.100 or otherwise a special web URL such as http://speedtouch.lan
No.3 Within the router next look for the security protocols such as WEP, WAP, WAP-PSK or better still I recommend you use WPA-PSK2 if its available because this provides tougher encryption.
**WPA-PSK2 requires that you create a complex long pass phrase for example:- "I love the smell of lavender & honey suckle in the spring". YES! feel free to use this statement if you wish but if you create your own then write it down and keep this secure for future reference. This statement is then used to create the encryption key, and the longer the key the harder it is to hack or crack.
**Your machine should also have an SSID (this is just a fancy name for a network ID label which is visible to the public facing internet). Mines called one hand clapping for example.
No.4 Once you have enabled WPA-PSK2 encryption and created an SSID most hackers will scan your network (router) and will quickly see it is securely locked down and go else where for easier pickings. The encryption key makes it extremely hard to almost impossible to brake your security and gain access to your network. Its NOT 100% impossible but lets put it this way a hacker is NOT going to waste hours & hours trying to gain access to a local domestic wireless network if there is little or nothing of real value worth stealing. They are after much juicer pickings is my guess and they will hack business networks because the returns are going to be higher in financial value. Your security is a deterrent like a burglar alarm is deterrent it works if the thieves go else where.
Hope this makes sense?
Kind Regards Ivan
20 years of computing. (from MS-DOS to Vista and more).