If you’ve gotten a new Mac, you do have to make some te it is safe and sound. Looking at https://www.tomsguide.com/us/best-antivirus,review-2588-6.html the big thing is to find a decent antivirus program and then install the following
- Avast which is free and well rated
- Turn on the firewall in system preferences/firewall
- Make sure that you have FileVault turned on disk security. This is how the default in high Sierra installs
- Install ublock origin for safari.
- Make sure your passwords are strong and install 1Password with Dropbox integration to have a central place