I was amazed to see someone on a forum publishing my IP Address and OS Platform etc. How can I prevent this happening? And how does a person obtain this information? What is more, what can they do with this?
This is normal and nothing to worry about. All computers transmits their IP address, and can be gotten very easily. Anything you do online can be tracked to your IP addresss. It can be used to track your local ISP's (internet service provider) location. It's no different than having a return address on a letter in the mail.
You can read more about IP addresses at the link below.