On the news this morning he told them to stop, I bet you feel safer now. If he feels that wasn't tough enough he will tell them again but louder that should do it.
As I understand it, Congress was informed of the Russian election hacking, and there was a stalemate as Democratic members of Congress wanted to release the information, while GOP members thought such revelations would unduly influence the election. Also, there was some disagreement between the FBI and the CIA about the extent of the problem (I've heard they've since compared notes and come to a consensus).
I think President Obama was somewhat hamstrung by the above political realities.