How you can block websites, not email file hosts? (C#)

To avoid anything on the computer from going to a website you virtually are tied to either:

  1. Network Proxy
  2. Network Driver (like peer guardian's approach, that is essentially packet inspection)
  3. You could attempt to include the website towards the no-reliable zone on your pc, however i don't believe chrome/ff/etc... give consideration to home windows security zones.

OpenDNS.Com is among an array of ways you can start obstructing sites. See their solutions overview to learn more.