Using the iPhone 4s, as a USB personal hotspot.

[WallyTheConfused]

Hi All.
I am in Spain, and have just bought an iPhone 4s, to use as a USB personal HotSpot, from my boat.
Long complicated story.. Anyway..
The menus are very confusing and some, seem to be repeats.
In one part of the menu, it says Wi-Fi Password ...............
Below that, there are three options.
Connect Using WiFi
Connect Using Bluetooth
Connect using USB

Anyway I plugged in the USB, and somehow got connected, straight away.
I have turned Bluetooth and WiFi off, and set phone to never lock ( while in use as USB ) so I can see I am the only one connected. So Far- So Good.

Now, as regards security, Where it says ; WiFi Password .. Is it the same, for Bluetooth and USB ?
Or is that password only for WiFi ?
If so, How do I set a password, for the USB connection ?
The reason I ask, is because, I just read an article, saying most Apple Hot Spot Passwords can be hacked in 50 seconds
Cracking iPhone Hotspot password in 50 Seconds

OK my WiFi password is 12 randomly generated letters & numbers, But as said, thats in WiFi, Nothing is mentioned for Bluetooth or USB.

Any explanation, in simple terms, will be greatly appreciated.
Thanks In Advance
Wally