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 Outside the Box matches this definition. Here's and why this matters.

What happened?

Israel disrupted Syrian air defense networks (with some collateral damage to its own domestic networks) during the bombing of an alleged Syrian nuclear facility.