Here is a real life reason why having an open WiFi connection can be a bad idea.
Recently a customer called in and explained that their credit card system was down. That’s pretty serious and we wanted to make sure we get them up and running as soon as possible. Our support guys started checking the usual suspects and discovered that the store could load a web page and could even log our technician in over the internet. We checked our credit card settings and the services that are running there and everything looked great.
They then decided to troubleshoot by bypassing SP-1 and running the card directly in the processors software. The card still did not go through. The next step was contacting the merchant services company that they use. It turns out that they are one of our preferred providers so we had an easy time of eliminating that as an trouble spot. That usually leaves an internet connection as a problem but we already confirmed that the computer was connected (heck, we were logged in remotely!).
Finally after running some more tests, we discovered that this had nothing to do with the computers, our software or the merchant services at all. It was the ISP (internet service provider) that deliberately blocked this type of internet traffic!
You see, at the store, there was an open WiFi connection for customers. This was simply enabled by turning on WiFi on the router. There was virtually no security activated at the router side. Because of this, someone using that connection was downloading things that the ISP flagged. The ISP started turning off activity from certain ports. That stopped the activity from the downloads but also from the credit card interface.
If you use WiFi, have a company like www.webbeams.com set it up for you so it can be secure!