Since it's using 802.1x and not simply a PSK then it's a lot more secure than what you'd think.

MAC addresses can be spoofed and BSSIDs can be figured out. The only real security in *any* wireless network (regardless of it's VHF, UHF, or higher like 2.4/3/5.8/10/20/24, is a strong pass phrase and additional measures such as using 801.2x/RADIUS.

Obviously stores POS systems are some how connected to the same LAN as wireless devices since Wal-Mart CSMs can price-override with their handheld now instead of using a physical key and a scan code. Of course, ACLs should also be in place allowing only proper devices to talk to the servers.


Jeff
Lead Field Engineer, MSCNS