This Wall Street Journal article tells the story of the massive TJX information theft which may have compromised as many as 200 million credit card numbers.

How did it happen? TJX did not have basic wireless security installed to protect the wireless data they were sending between hand-held price-checking devices, cash registers and the store’s computers.

The $17.4-billion retailer’s [Marshall's] wireless network had less security than many people have on their home networks, and for 18 months the company — which also owns T.J. Maxx, Home Goods and A.J. Wright — had no idea what was going on.

investigators now believe, hackers pointed a telescope-shaped antenna toward the store and used a laptop computer to decode data streaming through the air