They would rather use that POTS (Plain Old Telephone System) to do transaction which is really more prone to tampering. A person could just simply tap to the two-wire line and connect a DTMF (Dual Tone Multi Frequency) decoder. The corresponding matrix of frequency will give a corresponding number pressed by the unknowing telephone line user.

Most broadband wireless will still use the “main line” of internet connectivity which are DSL, Cable, ISDN, and T1. Data will pass through the physical cable. Taking the DSL line as an example, the data are transmitted on the same POTS but on a higher frequency much more than the audio band of the normal phone. It uses a frequency shifting to represent a “1’ and “0”. Although a person can also tap on this physical wire, the data is more complex to decode.

The very first line of defense is your remote CLIENT and the controller HOST which is connected to the main line. The data going through and from the remote to the controller is highly encrypted that only 0.5% of the world's population can decrypt it. Don’t worry!! those people are protected by agency or government and they are bind by restriction when dealing with cryptology. One more thing, you are just a "hay on a hay stack within a hay farm" so those guys will not spare their time cracking your data if they see that its not that profitable. And besides, they are busy protecting themselves from their own kind.

The simplest way to protect your data is to use a directional antenna so that few people can only "see" your signal. This is synonymous to a highway. You build you road going to a particular place and other area have no access to your road unless they put their own place along your highway. You can simply transport your cargo to and from that particular place to your own place using your road.

Since wireless connectivity should always be on, you can turn off your broadcast ID just in the case of WIFI which is using an SSID. The link is present between your client and the host but other can’t see what is the link name. Going back to the highway, it’s similar to turning off your street light so others can’t use it. The remote knows the road properly even without street light because it is already program on its system.

You can add filter on your wireless connectivity. A MAC filter is one the most common way of securing your network. This is the Hardware ID of a machine. This is like the house address along your highway. When you send you cargo, the transport media locates this address to see if there is a  match on stored list. Without this address, the user on that area can’t use the road or the transport media will not deliver any data to this.

If we take WIFI, a simple security implementation is the WEP. A code key is provided to every address on the network so that it can access and use the network. Advancement in wireless technology as in  the case of WiF produced  WPA, WPA2 with AES encription.