Is Google Voice susceptible to hacking like regular MMS or Whatsapp messages?
Google Voice, aka Hangouts, is fully encrypted point to point.  If you've posted anywhere with your Gmail account, you could have a message pushed to you.  Unless you have OS 6-10 you'll need an &quot;anti-spam&quot; app HIYA is a very good one. The newer OS have been given the ability to flag calls &amp; SMS - MSMs as spam.
Good luck.