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OpenDNS provide free porn-blocking DNS servers

Installation requires switching the DNS servers of your router or device to use the OpenDNS ones. If you create an account, you can customise the degree of filtering and view some simple stats.

This is useful for home networking when you have kids. Unfortunately, the Virgin Media Hub 3.0 I have doesn’t support custom DNS settings - you need to use it as a modem with a separate router to achieve that. Still, I can switch the DNS on all house devices.

See https://www.opendns.com/home-internet-security/ for more.