Public wifi

Like any radio signal, wifi can be received by anyone within range. So, what’s to stop a third party from parking outside your house and watching you surf the net, do your banking etc? The answer is encryption. Home and work networks are usually encrypted so that any eavesdroppers would only receive an unintelligible jumble of characters.

Unlike your home or office wifi, most public wifi networks are not encrypted. If you browse to a site that doesn’t start with ‘https://…’ it is very easy for someone to eavesdrop and see all the information being sent between you and the website that you are on. This is called ‘sniffing’ and is virtually undetectable.

Fortunately for us, a lot of sites do use SSL (https://…) that further encrypts the actual information traveling between your browser and the website, even though the network itself may not be encrypted.

A skilled hacker can still get around this, for instance, by pretending to be the public wifi hotspot and thereby forcing all your traffic to route through their computer first before getting to the public wifi. This is called a ‘man in the middle’ (MITM) attack. By inserting himself between your computer and the open wifi network he can force your computer to use unencrypted information (http://) or he could mess with the certificates that SSL (https://) uses.

The takeaway is that you should avoid doing sensitive browsing (online banking etc) while on a public network. While on public wifi you should also make sure you only send sensitive information to sites that have https:// at the start of their address. A handy tool to make sure that your browser uses SSL (https://) whenever possible is available for free: it’s called HttpsEverywhere.

For the ultimate protection against eavesdropping you could use a VPN (Virtual Private Network) service. If you’re fairly technical you can set up a free VPN using the OpenVPN service. Paid VPN services like GhostPath are somewhat more reliable and easier to use (affiliate link below).