While waiting for the train at the station, I decided to try using the WiFi Master Key to see how effective it is. Surprisingly, I was able to connect to the network. Although this is convenient for passersby, it also comes with risks that many router users are not aware of.

After understanding the principle of the WiFi Master Key, I realized that when a user connects to a network and chooses to share it, the server of the Master Key will remember the SSID. When other users connect to the same SSID, the server will check if it has saved the password for that SSID. If it does, it will provide the password to the new user. If not, it will attempt to crack the password (though the Master Key usually only tries common passwords, so it's not a true brute force attack) which often fails. However, the actual principle of the WiFi Master Key may not be as simple as I imagined. I simply analyzed it briefly. In any case, when using it, there is a high possibility of leaking your own WiFi password and making it convenient for others to use.

When I was at home, I took out my phone and found my neighbor's WiFi. I was able to easily connect to it using the WiFi Master Key. This indicates that other users have connected to these SSIDs and entered the correct passwords, which suggests that the WiFi password of my neighbor has likely been leaked through the Master Key, allowing me to easily connect to it.

In this situation, I couldn't guarantee the security of my own WiFi password, so I quickly opened the router settings interface and made some changes to prevent others from easily using my network. Here are a few suggestions:

1. Change the default username and password of the router

By default, the username and password are often set as "admin," which is extremely insecure. It is strongly recommended to change them. You can do this in the "System Tools" and "Modify Login Password" sections.

2. Disable SSID broadcasting

By default, the router broadcasts the SSID, making it easy for others to find your WiFi signal and potentially leak your WiFi password. You can disable this feature and manually set up wireless network connections. This can be done in the "Wireless Settings" and "Basic Settings" sections. This way, others cannot connect to your WiFi unless they know the SSID name.

3. Enable wireless MAC address filtering

You can enable this feature in the "Wireless Settings" and "Wireless MAC Address Filtering" sections. The "Prohibit" option can be understood as a blacklist, while the "Allow" option is a whitelist. The MAC address can be found by using the "ipconfig /all" command.

Of course, router security settings go far beyond these. The above suggestions are just some commonly used practices. It might seem a bit troublesome, but it greatly improves security. The WiFi Master Key is a useful tool, but it also poses risks. Therefore, when using it, one should be extra careful and avoid connecting to one's own home network using the WiFi Master Key, as it may lead to password leakage.