How to make a free minecraft sever without downloading viruses?

Download the server files from their official site - https://minecraft.net/...t/download

Run the server which will create all the files needed. Open up your config, check/add the IP and port (make sure you port forward on your router otherwise people can't join) then run the server again and people can join by using the IP and port.

There are many many tutorials on YouTube which explain it better due to me being limited to text and a character limit. You can also use http://portforward.com/ to help you with the port forwarding.