Yes

A cyber attack is a cyber operation, whether offensive or defensive, that is reasonably expected to cause injury or death to persons or damage or destruction to objects.

Michael Schmitt et al; Tallinn Manual 1.0, pp 92
  • Cyber Operation?
  • Expected to cause death or injury to people or objects?
Operation Glowing Symphony matches this definition. Here's and why this matters.

What happened?

Joint Task Force-Ares is the U.S. Cyber Command/NSA/MARFOCYBER joint task force which conducted Operation Glowing Symphony against ISIS, working hand-in-hand with the kinetic operations (support lethal fires) as well as conducting collection and information operations as part of Operation Inherent Resolve, the global coalition tasked with ridding the group from Iraq and Syria.