You can password protect your TeamSpeak 3 server either through the TeamSpeak 3 client, or from the control panel.
To do this from the TeamSpeak 3 client, please do the following:
Right click on your "Server Name" at the top of the TeamSpeak 3 window and select the "Edit Virtual Server" option.
In the "Password" input box you'll type in the password you'll want to use for people that are connecting to your server. Once you have the password typed in click the "Apply" button at the bottom of this window.
To do this through the TeamSpeak 3 control panel, please do the following:
1- Login to your TeamSpeak 3 control panel.
2- Click "Game & Voice Management".
3- Click "Voice Services".
4- Under "Actions", click "TeamSpeak Browser". Your server port and name will now appear.
5- Under "Settings", enter the password in the "Password" box, and click "Save".
If you have any trouble, please be sure to open a support ticket to contact us so we can investigate.