The FBI and Microsoft have seized more than 100 web domains they say Russian intelligence used for cyber-espionage, according to court documents unsealed Thursday.

The domains were alleged to be staging grounds for Russia’s FSB intelligence agency in its ongoing efforts to spy on targets of interest, ranging from the U.S. Energy Department to Russian nonprofit groups and media outlets critical of the Kremlin.

The FBI said in an affidavit that the websites were used as part of a “spear phishing campaign,” a term for targeted efforts to trick people into divulging sensitive information, usually email login credentials. That information was sought “with the goal of gaining unauthorized access to the computers and email accounts of victims, to then steal valuable information and sensitive United States government intelligence,” the FBI said in the affidavit.