What files should be deleted if i don't want anyone to know if the system has been once linked to the internet?

For certain reasons I have to delete all files that might indicate that the syatem has once been linked to the internet. I have deleted all the records in browser, and the internet ethernet address. What else I can do, such that no one is able to know that the system has linked to the internet? Can I delete all files in var/log? This is a new system with only the anaconda and relavant pachakges been installed.