For the first time since the December 2 attack, Comey made a definitive connection between the couple and ISIS though he was unable to give many details on the nature of that connection.
"There is some indication that they were at least in part inspired by ISIL," Comey said.
Comey noted throughout the hearing before Senate Judiciary Committee that this couple had been radicalizing before the rise of ISIS.
Asked whether the marriage of shooters was arranged by a terror group or terror operative, or was just a meeting of two radicals online, Comey said: "I don't know the answer to that yet... It would be a very, very important thing to know."
Comey said they were talking about jihad and martyrdom before they became engaged and started living together.
"We're working very hard to understand exactly their association and the source of their inspiration," Comey said. "We're also working very hard to understand whether there was anybody else involved with assisting them, with supporting them, with equipping them. And we're working very very hard to understand, did they have other plans? Either for that day or earlier, and that work continues."
Farook, 28, was born in the United States and Malik, 29, was born in Pakistan.
She first came to the U.S. with Farook in late July 2014, arriving on a K1 fiancee visa. Court records state that the couple was married in Riverside, California on Aug. 16, 2014.
Police identified Farook and Malik as the two suspects hours after the December 2 shooting, which left 14 people dead and 21 others injured.