U.S. District Court for the District of Columbia court documents The criminal complaint filed Friday reveals more details about Cherkasov's life undercover, from his time spent creating a false identity in Brazil more than a decade ago to applying for jobs in the U.S., including some that required a security clearance.

In 2010, years before his arrest, Cherkasov assumed his new identity in Brazil after obtaining a fraudulent birth certificate, according to court documents.

His supposed late mother was a Brazilian national and he spent a lot of time with his aunt, who spoke Portuguese poorly and liked showing him old family photos, according to a document that contained details of his cover that were found with him when he was arrested in Brazil.

Near the end of 2021, Cherkasov was allegedly sending messages about U.S. policy on Russia's potential invasion of Ukraine to his handlers.

The messages to the handlers included details on his conversations with experts and information he had gleaned from online forums or reports about Russia's military buildup near Ukraine's border and NATO, court documents said.

After his arrest, Brazilian authorities gave the FBI covert communications equipment recovered from remote locations in Brazil that Cherkasov had allegedly hidden before his departure to The Hague.