They have been releasing warnings like this on and off for months. We really need that context, because we've gotten a lot of false warnings prior to this one which was spot on. Of course, they've not explained the underlying intelligence that lead to these warnings and what made a difference here.

For me, the second I heard them blaming ISIS, that was sort of the nail in the coffin. ISIS is an Obama creation. It is not organic. It is literally a CIA product. We radicalized and organized them. Trump shut them down, Barry Soetoro 2.0 brought them back. And that's if you believe this narrative. Personally, I'm with Medvedev on this one.

I strongly suspect it was Ukraine, which has routinely been sending in operators to conduct sabotage operations, launch drones, set up car bomb assassinations, etc. Russia has an excellent track record of catching these people with extreme prejudice and frankly that's exactly the way you have to police such things: overwhelming force. I strongly suspect it was Ukraine. The only thing working against this theory for me is that Russia has such good intel on what they do, it almost seems more plausible that this successful attack had to come from outside those typical channels: Russia has them all surveilled.

Regardless of initial suspicions, the 24h rule needs to be in force. We need more information to know. Right now, we're just speculating.