No

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 damage to objects?
Russian Defacement of Several Ukrainian Websites does not match this definition. Here's a list of actual cyberattacks and and why this matters.

What happened?

A number of Ukrainian government websites including the Ministry of Foreign Affairs, Cabinet of Ministers, Ministry of Education, Emergency Services, Treasury, and the Ministry of Environmental Protection were defaced by Russian actors likely associated with the GRU.