There are a few problems with using a public Wi-Fi network. The open nature of the network allows for snooping, the network could be full of compromised machines, or the hotspot itself could be malicious.
While using a public WiFi could have its advantages, it is advisable not to use it for online banking
Snooping
Encryption normally helps protect your network traffic from prying eyes. For example, even if your neighbours at home are within range of your Wi-Fi network, they cannot see the web pages you are viewing. This wireless traffic is encrypted between your laptop, tablet, or smartphone and your wireless router. It is encrypted with your WiFi passphrase.
When you connect to an open Wi-Fi network like one at a coffee shop or airport, the network is generally unencrypted — you can tell because you don’t have to enter a passphrase when connecting. Your unencrypted network traffic is then clearly visible to everyone in range. People can see what unencrypted web pages you’re visiting, what you are typing into unencrypted web forms, and even see which encrypted websites you are connected to — so if you are connected to your bank’s website, they will know it, although they would not know what you are doing.
More advanced tools like Wireshark could also be used to capture and analyse traffic.
