What was the classified Russian threat that spooked the US Navy?

via USNI News

Last spring an emergent need arose in the Mediterranean – a new Russian threat, the details of which remain classified, put the four Spain-based DDGs at risk as the ships focused on a ballistic missile defense target.
After looking at the threat and several possible options to address it, the Program Executive Office for Integrated Warfare Systems, U.S. 6th Fleet, the Surface Warfare Directorate and other organizations selected SeaRAM as the solution and got to work on the “quick reaction capability.”
Without discussing the nature of the new threat, Program Executive Officer for Integrated Warfare Systems Rear Adm. Jon Hill told USNI News on March 3 that SeaRAM was selected because “it allows them to have that additional layer – it’s a different missile system, it operates in a shorter range regime and it’s much more maneuverable, so it gives them a capability that complements the rest of the layers” of ship self-defense.

What did the Russians build that has the US Navy spooked?  I've looked at the open source stuff and I haven't seen word of a new, heavy weight anti-ship missile that could burn thru a DDGs current defenses....so what am I missing?