KidsHealth from Nemours describes the following as signs of cyberbullying - 

Many kids and teens who are cyberbullied don't want to tell a teacher or parent, often because they feel ashamed of the social stigma or fear that their computer privileges will be taken away at home.

Signs of cyberbullying vary, but may include:

  • being emotionally upset during or after using the Internet or the phone
  • being very secretive or protective of one's digital life
  • withdrawal from family members, friends, and activities
  • avoiding school or group gatherings
  • slipping grades and "acting out" in anger at home
  • changes in mood, behavior, sleep, or appetite
  • wanting to stop using the computer or cellphone
  • being nervous or jumpy when getting an instant message, text, or email
  • avoiding discussions about computer or cellphone activities