You sit in the laundromat, waiting for your laundry and suddenly see a sign with Wi-Fi access data. You don’t hesitate long and connect to the laundromat's public Wi-Fi. Why this might not be the best idea and what you should do instead, I will explain here.

No Privacy in Public Networks

Public Wi-Fi is for everyone, as anyone can log on, whether it's a customer of the laundromat or a hacker. A hacker can then spy on data by inserting themselves between the router and your device. This is possible because most public networks use no or only weak encryption, as they use outdated protocols. Thus, a hacker can intercept bank data or other personal information.

VPN – The Solution?

To surf safely on a public network, a VPN should always be used. VPN stands for "Virtual Private Network," meaning a virtual, private network. "Virtual" because the connection does not occur physically, and "private" because it is an encrypted connection. But what exactly is a VPN?

In simple terms, a VPN builds a secure connection with a server in a remote network. The remote network can be that of a company or a VPN provider. From this network, the data is then forwarded to its destination. The two central features of VPNs are firstly encryption, as a VPN transmits data only in encrypted form, and secondly hiding your IP address. But more on that later.

Example

Let’s provide a detailed example: You are in a public Wi-Fi and connect to a VPN. All messages are first sent to the server, also called the VPN server, in the network of the VPN provider or in the company network and from there forwarded to the recipient.

The task of the VPN server is to receive the message from the sender, convert the sender's IP address into its own IP address, and then transmit the message to the recipient. With this method, it is possible that the recipient does not see your IP address and therefore cannot identify your location. In the case of a reply, the connection proceeds in reverse order, that is, first to the VPN server and then back to the original sender. Of course, all traffic is encrypted throughout.

Advantages and Disadvantages

A VPN has the major advantage of protecting you from being spied on or attacked in public Wi-Fi by encrypting the traffic. This makes it difficult for hackers to read the data. Also, as mentioned earlier, the IP address is concealed, so the recipient does not see who the message originally comes from.

Another advantage is that geographical restrictions can be bypassed. With a VPN, you can access media content from other countries that you would otherwise not have access to. For example: A series is only available on a streaming service in Spain while you are sitting in Germany. Then you can simply use a VPN and connect to a VPN server in Spain.

Along with the advantages, there are also disadvantages: On one hand, absolute security is not guaranteed, as it is sometimes unclear which encryption method is used by the VPN provider. While other people cannot see your IP address or private data, the VPN provider can. This raises the question of how much trust you can place in the provider.

On the other hand, the internet speed over a VPN is sometimes slower. This occurs because the data first goes to the VPN provider and then is forwarded from there. Additionally, some countries block the use of VPNs, so they cannot be used there.

How does it work technically?

In short, a VPN uses the method "IP packet inside an IP packet." But let’s explain this in more detail: We have a packet. This packet includes the actual message, a sender IP address, and a recipient IP address.

Now let’s go through what happens step by step:

Before the packet is sent, it is first completely encrypted, and the recipient's IP address is changed to the IP address of the VPN server. The sender's IP address remains the same. The packet is then sent to the router in the network. The router converts the sender's IP address into a public IP address, that of the router.

Then the packet is sent to the server in the VPN provider's network. There, the packet is decrypted. In the decrypted packet, you can then see the actual recipient's IP address. The VPN server now takes the decrypted message, the recipient's IP address, and its own IP address as the new sender IP address and forwards the message to the recipient.

As we have seen above in the article, using a VPN is not a bad idea. While it also has disadvantages and you must trust the VPN provider, the advantages clearly outweigh the disadvantages. Protecting your privacy is very important, especially when it is not your own network, but a public one with an unknown owner.