Over half of public WiFi services being offered globally do not comply with the law leaving them open to misuse by terrorists and criminals, a new survey finds.

The latest Purple WiFi survey revealed that about 2048 of the overall 3,349 venues surveyed across the globe were completely running open networks or offered passwords, implying the network could be used by criminals without being tracked.

Purple WiFi CEO Gavin Wheeldon said that the international WiFi market is expected to be worth more than $93bn by 2018, but it has offered little in the way of value for the venues that provide WiFi.

"Customers expect free online access at venues and businesses wherever they are, and from today businesses can offer this service for free," Wheeldon said.

About 58% of the overall venues were not equipped with content filtering systems or were not aware of if they did, indicating free access to open or illegal websites via the WiFi connection.

In addition, 82% of the surveyed Wi-Fi venues deem they meet the terms of the law, the cloud-based Social WiFi software claimed than roughly only 40% do.