My sons father has never been in his life and never so much as bought a diaper whip for him. He has now moved out of state and ORS cannot find him. I want to change my sons last name to my last name. I also want to make sure his biological father is unable to take him from me legally. What do I need to do?

Yes, its abandonment but its not something you can prosecute for. You can't force a father to be a father.

What you need to do, is go to court and request a legal name change and full legal and physical custody. You will have to show you have tried to serve him with notice of the court action. But if he doesn't not respond, it should be granted.

You can't ensure that he can never show up and try to get custody. But it will be difficult for a court to approve anything more than supervised visitation if he shows up out of the blue. Courts allow for someone changing. If he shows up, he will be given the chance to show he has changed.