Public wifi networks at cafes and public spots can be a risk because they may not require authentication to establish a network connection," explains Dr Suelette Dreyfus, a lecturer at the University of Melbourne's School of Computing and Information Systems.

"An intruder may be able to slip in between your laptop and the network. If you are file sharing on a network, perhaps he inserts a malicious piece of software. Or maybe he just eavesdrops, slurping up your credit card or personal information sent over an unencrypted connection.