This article explains how to change the default admin password of your wireless router. It applies to all routers.
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Hackers have been breaking into wireless networks for a long time, but they don’t need to hack into your wireless network if you’ve never changed your wireless router’s admin password from the default. All the hacker has to do is find the default password and log in.
To change the default password, open the admin console in a web browser, enter the default router password, and look for a field labeled password or something similar. Instructions vary by router brand and model.
You need to know the default password to change it. If you didn't write it down when you set up your router, you can find it in the documentation that came with your router or on the manufacturer's website.