^Its default. It can be changed also.
@MM: Enter router settings by entering default gateway IP in browser. Default is 192.168.1.1. If you don't know it, run ipconfig /all from cmd. There, check out for default gateway.
Now enter that in browser and enter the default ID/pass as written in router's manual.
Go to wireless/security tab and enter a desired pass. Keep it strong as its your only reliable weapon. Enable WPA2 / AES protection, and along enable MAC filtering if possible.
Change default gateway also plus the admin pass.