How does a VPN work?

Question

I’ve heard the tunnel explanation before, but it’s just not doing it for me. What’s going on with the packet and the addressing itself? Traffic still has to go to my ISP before it can get anywhere else, so how is the VPN able to obfuscate my IP address and location?

In: 4

Answer 1

#ELI5

You want to write a letter to your friend Jason.

So you write your letter, and put it in the envelope. You write Jason’s name on the outside. You give it to the post office. The post office reads the address, and delivers it to Jason.

But now all the guys at the post office can read the address. It’s right there in the open.

And if the police stop by, and demand to see today’s mail, they can see that you sent a letter to Jason too.

HOW DO YOU COMBAT THIS?

You hire a middleman. We’ll call him Pete.

You make your letter to Jason, and put it in the envelope, and put Jason’s name on it … BUT THEN you put that envelope in ANOTHER envelope, with Pete’s address.

You paid Pete to open the mail, and deliver the contents to whoever is on the inside envelope.

Now all the guys at the post office know you sent mail to Pete, but they have no idea you sent mail to Jason.

REPEAT this process: First a letter to addressed to Jason, inside a letter addressed to Pete, inside a letter addressed to Elizabeth … you can see how it becomes more and more difficult to know that you sent something to Jason.

BUT BEWARE. The fact that you sent mail at all, is still known. The fact that your return address is on the outermost envelope, is still known. Your ISP still knows that YOU sent “data”. And it knows you sent it to the the VPN! But that’s all it knows. It doesn’t know the final recipient, or the contents of the data.

Follow-on:

There’s tons of tricks to obfuscate things further. Like, when Pete sends your letter on to Jason, he can make it look like it came from Pete, not from you. So Jason could be unaware it came from you. So Pete is doing more than just forwarding, he’s changing the “From” address on the outside of the envelope.

THIS IS VERY BASIC. I know people are going to point out some shortcomings from this explanation. But this is, after all, ELI5.