The FBI's case against an alleged deep cover Russian spy ring relies heavily on surveillance of their use of ad hoc Wi-Fi networks, bespoke software, encryption and the web.
After a counter-espionage operation lasting several years, 10 people were accused on Monday of being covert agents of the SVR, Russia's foreign intelligence service. An 11th alleged member of the network - dubbed the "Illegals" programme by investigators - remains at large.
[A man has been arrested - see update at the end of this article.]
Anna Chapman, from her Facebook page
The criminal complaints against the group highlight their dependence on internet technologies.
Testimony from FBI agents describes how 28-year-old Anna Chapman (pictured) allegedly kept discreet appointments with a Russian government official at Manahattan coffee and book shops. Without making overt contact, she would allegedly communicate with her handler over an ad hoc Wi-Fi network.
"Russian Government Official #1 was across the street from the book store, carrying a briefcase," an unnamed FBI agent says in the complaint.
"I observed Chapman pull a laptop out of the tote bag. Chapman stayed in the book store for approximately thirty minutes; Russian Government Official #1 was in the vicinity of the book store (but outside) for approximately twenty of those thirty minutes."
Chapman allegedly kept 10 such appointments on Wednesdays between January and June this year. On nearly every occassion the FBI observed the same two MAC addresses communicating via ad hoc Wi-Fi.
Surveillance agents nearby used "a commercially available tool that can detect the presence of wireless networks" to witness the creation of the ad hoc networks. NetStumbler is probably the most popular example of such software.
"Law enforcement agents were able to detect a particular MAC address - MAC address A - at the time that Chapman was observed powering on her laptop computer," the complaint says.
"Law enforcement agents were also able to determine that the electronic device associated with MAC address A created the ad hoc network."
Chapman's fellow defendant, Mikhail Semenko, is accused of similar data exchanges with another Russian government official in Washington DC.
On one occasion in April, the Russian government official, who was based at the UN, rumbled his surveillance team, according to the court documents. He returned to his office and only one of the usual MAC addresses, allegedly belonging to Chapman's laptop, was observed trying to communicate.
On Saturday last week she handed the laptop to an undercover FBI agent, "so that it could either be fixed, or sent back to Moscow". An hour after the meeting she allegedly bought a Motorola phone and international calling card under the name "Irine Kutsov" of "99 Fake Street". The following day, last Sunday, she didn't turn up to another scheduled meeting with the undercover agent.