Islamic State Khorasan (IS-K) has taken credit for attacks by other terror networks in the past, but it is almost certainly behind the deadly assault in Russia, though nothing is impossible.
The group has claimed responsibility, and the chatter picked up by Western intelligence services in the days leading up to the atrocity also indicated something was coming.
The Talibanis now regularly engaged in combat against IS-K, as it threatens its ability to govern Afghanistan.
But unlike other terror groups, IS has transnational ambitions.
Counter-terror officials have foiled numerous attacks in Europe in recent years.
Russia is of particular interest to the group and would have been targeted because it claims President Vladimir Putin and his regime are killing Muslims.