You can tell if your computer is safe in a few ways.  One way would be to ensure that all devices, drivers, and updates are always current and up to date.  Installing a really good computer security system will help malware to walk its way into your computer, thus ensuring that your digital assets are safe.  Scanning and checking your antivirus will periodically ensure that your computer is safe as well.  You can also ensure that your computer is safe by turning off services like wifi and Bluetooth whenever it is not being actively used.  This will safeguard your computer from criminals exploiting the connection into your computer via wireless means.  Also, do not turn on any sort of automatic connection to wifi and/or Bluetooth.  This will force you as the user to physically connect to a wireless platform of your own volition, and it will also not automatically connect to something other than what you intend for your computer to connect to.  Whenever you download any file from the internet, do so securely.   Whenever you browse the internet, it is best practice to use HTTPS, which is much more secure than HTTP.  Another important check is to make sure your firewalls are on and only trusted sites to the user allow pop-ups and other services on the internet.  You can ensure that your computer, and in tandem your information, is safe by connecting a backup hard drive and copying all important files on there.  This way if your computer is ever rendered not safe, you are not going to be predisposed to a ransomware attack.  A user can ensure their computer is safe by running a URL filter.  This would block URLs from known hosts of malware, spam, and malicious content.  A paid antivirus software should be able to execute this function, which will help keep your computer safe.  Another way to ensure your computer is safe is to ensure nothing is plugged into it that should not be plugged into it and to update and change your passwords often.  Never use the same password for multiple services.  Lastly, be professionally paranoid.  The more you ask questions about random emails or messages from people that you think are who they say they are, but there is something off about the message, the better off you will be.  This will help the user keep the computer safe on a continuous basis.