There are a few ways an Invasion of Privacy can occur that gives rise to liabilty:
Intrusion Upon Seclusion - This is when an uninvited person intentionally thrusts him or herself into another person's private affairs or place of seclusion in an offensive manner.
Appropriation of Name or Likeness - When someone else uses your name, image or identity without permission and for commercial gain.
Public Disclosure of Private Facts - The breach of a duty of confidentiality, publication of wrongfully obtained information, publishing private information in a socially intolerable manner or a false report about a person's private affairs.
Invasion of Personal Privacy - Peeping Toms aren't just a joke to be made on television. If your privacy has been intruded on, you know how serious a matter it is.