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?
US Operation to Disrupt Iranian Missile Launch Control matches this definition. Here's and why this matters.

What happened?

The U.S. announced it had launched offensive cyber operations against Iranian computer systems used to control missile and rocket launches.