Fortunately, most reputable online therapy services have FAQ pages where you can find a simple rundown on patient privacy and security policies. One thing these should touch upon is HIPAA.
At a bare minimum, your online therapy service should be HIPAA-compliant (that's therapist-patient confidentiality, among other things). The service you choose should also let you verify your therapist’s and your own identity. Additionally, you should check that the service is verified by the American Telemedicine Association.
For video therapy, these compliances and verifications ensure your session isn’t being recorded and cannot be accessed by any company. For the record, Skype, FaceTime, and Google Hangouts are not HIPAA-compliant platforms.