Is someone using my internet?

I was watching videos on my Iphone then I notices a button at the right bottom corner, here is what it said;

Iphone
Andrew's Macbook

I noticed that there's no Andrew in my family. What does this mean? Is someone using my internet? If so what should I do?

Added (1). I already have a password setup for my router btw.

Yes lol. One of your neighbors is stealing your internet.

What you should do is change you Wi-Fi password. If you need help doing this just ask me and i will help you out.

Yes! Someone is using your internet. To stop this you should make your Wi-Fi password restricted that only you and your family know. That will solve the problem same thing happened to me.

Put a password on your router. I would do this As soon as possible. (I would unplug the phone line from the router until you get that setup, that will really bug them as they wonder why they can't connect).

Macs are very social. They can detect each other even if they're not actually sharing anything. You can set a Wi-Fi password if you haven't already, but if it doesn't go away, it's just a figment of a Mac's imagination.

(Meaning, you may have to turn off weird stuff that may not be worth it like UPnP on your iPhone, and lord knows where that setting is!)

Change your password.

Just because you see another name there does not mean someone is using your internet, more than likely it is just another signal from someone else who has a wireless connection. It is showing up because they are within your range, which is usually about 500 FT or less. Where I live I show a connection named "Michael" with a medium signal range which means this person lives about 250 - 300 feet from me, another named HARO56 is another user, very poor signal which means this person is probably about 450 - 500 FT from me. If you have a password set up this should be nothing to worry about. Incidentally, when you click on this name what happens? Does it ask you to connect? Does it ask you for a network security key? If so then you are safe. Just as an extra precaution, if it makes you feel better you can always change your password as well. That is up to you.