A while back I posted on the dangers of guest WiFi in your office, today’s article will relate more to folks who use free public Wifi available in coffee shops, airports, malls and so on. While these services are great and will save you money on mobile data, they aren’t without their dangers and downsides.

Sniffing and Snooping

When you join any sort of network, communication takes place on a number of levels (known as network layers). The layers that you as the user would see, are on the application level, and to an extent the protocol; such as seeing HTTP or HTTPS in the address bar of your browser.

Below these layers, are the network layers, the unseen side of how communication happens between your laptop and the internet (or any other computers). These layers pre-date a lot of the security we’ve seen in recent years, and as such are vulnerable if a malicious person is on the same network.

On these lower levels, if another person in the coffee shop decides to scan the network, they will be able to find your computer on the network with relative ease (sniffing) and be able to insert their own computer between you and the internet or hotspot without you knowing (snooping). They can then capture everything you do onto their machine for later (mis)use.

Decrypting Network Traffic

With any luck, you will be connected to a hotspot with something called guest isolation, where computers connected to the hotspot cannot “see” each other. More often than not though, this will not be the case.

When you join a hotspot, if it is “open” there is no encryption on the connection, however when a key or passphrase is required the WiFi is seen as more secure. However, while these phrases do encrypt the network from the outside, they are known to anyone else connecting too – which means a malicious hacker could join the network and decrypt the traffic on the network with the same passphrase.

This is one of the core reasons why a public network is a rather lawless place, anyone can get the keys, and anyone can start decrypting traffic.

The Importance of Secure Protocols

This is not to say it is all gloom and doom, modern day protocols such as HTTPS are a second layer of encryption on your public network – so if a hacker decrypts your connection, they don’t necessarily have access to what you have transmitted. This is where the importance of certificates and seeing the green security padlock in your browser comes in; if you don’t see it, don’t submit ANYTHING on that network.

Browsing via HTTP/HTTPS is the protocol that most folks are aware of, however your machine uses other protocols too. Things like your email and instant messaging run on protocols too, with the former often insecure (POP, IMAP and SMTP). For this reason, connecting to a service such as a VPN is valuable.

Additional Security

If you are part of a corporate organisation, chances are you already have a VPN available to you, ensure that you have it set up and that you use it when on a public network. Reach out to your IT department for more details.

A VPN encrypts everything you are doing into a form of tunnel, something that a hacker cannot easily break into, securing even your insecure traffic. The caveat is however that the VPN provider would still potentially be able to see your insecure traffic – so it’s important that you choose someone reputable to provide yours. Many third party providers exist for this purpose, such as NordVPN or WebRoot (this is not an endorsement of either, this is just a listing of two services I am aware of).

In short, using a public WiFi without any form of additional security could land you in hot water without realising it. Be sure to always use secure protocols like HTTPS when you are browsing, or get yourself a VPN to secure your whole connection from end to end. It’s a small price to pay for the peace of mind provided.

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