Recently, federal authorities announced the arrest of 10 spies. While this happens from time to time, what has made this case noteworthy is the use of private, peer to peer (also known as ad-hoc) wireless networks used by the alleged spies as well as other advanced data hiding techniques.
The federal complaint, available at Scribd or at mainjustice.com, discusses how temporary networks were alleged to have been used to allow the spies to secretly move data without physically meeting. For example, there is a mention in the government complaint that a secret appeared to be passed between one spy in a bookstore and a second spy that was standing on the street.
As the communications were not done directly through the Internet but through these temporary networks, agents needed to be physically close to the subjects. Since the wireless signals are usually limited to 300 feet from transmission to reception, investigators would either need to be near the spies or would need a specialized antenna that could increase the signal strength. Either of these options could be obvious.
In this complaint, MAC addresses were used to identify the potential spies. A MAC address is basically a unique identifier for a computer or smart phone when it is using a wireless network. Since these addresses are unique, the federal agents were able to detect that a network was being set up between the same two individuals repeatedly over a six month period.
This complaint shows a high level of sophistication by the alleged spies and by the FBI. This should prove to be an interesting case as it wides through the legal system.