How can I block some websites in Windows 8 without using any tools or third party firewalls?
If you are admin on a windows pc, and want to limit internet access to another user on your pc, you can look into internet explorer's
Content Advisor feature. It allows you to block specific sites, unless a supervisor password is entered. But, one flaw this method has is, if the user has other browsers installed, s/he can access the blocked sites with out a problem. But, you can almost prevent installation of software by putting some more limitations.
See this for FAQ on content advisor.
This HowToGeek article explains how you can make Windows Defender block certain host files.
It uses Windows Defender's option to Exclude files and locations:
and editing the hosts-file in your C:\Windows\Systerm32\Drivers\etc\hosts folder
Check the article for more details