Criminal complaints filed in federal court on Monday read like a thriller novel: Secret Russian agents were assigned to live as married couples in the United States, even having children who were apparently unaware of their parents’ true identities. A spy swapped identical bags with a Russian official as they brushed past each other in a train station stairwell. Messages were written with invisible ink, hidden in the data of digital pictures, and encoded in messages sent over shortwave radio…

It added: “Illegals often operate in pairs – being placed together by Moscow Center” – the S.V.R. headquarters – “while in Russia, so that they can live together and work together in a host country, under the guise of a married couple. Illegals who are placed together and co-habit in the country to which they are assigned will often have children together,” further establishing their cover.

According the the charges, the agents would communicate back to Moscow using such techniques as stenography – including secret encrypted data in an image that could be posted on a publicly available website but would appear unremarkable to the naked eye; radiograms – coded bursts of data sent by a short-wave radio transmitter; and setting up wireless laptop computer networks in public places.