Blocking websites

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There are several options for blocking websites with pfSense, some of which are described on this article.

Using DNS

If the built in DNS Forwarder or DNS Resolver are in use, an override can be configured which will resolve the website to block to an invalid IP address (such as 127.0.0.1).

Using Firewall Rules

If a website rarely changes IP addresses, access to it can be blocked using firewall rules. This is not a feasible solution for sites that return low TTLs and spread the load across many servers and/or datacenters, such as Google and similar very large sites. Most small to mid sized websites can be effectively blocked using this method as they rarely change IP addresses.

A hostname may be entered in a network alias, and then that alias may be applied to a block rule. Note the hostname will only be resolved every 5 minutes, but that may be changed under System > Advanced on the Firewall/NAT tab (Aliases Hostnames Resolve Interval).

Another option is finding all of a site's IP blocks, creating an alias with those networks, and blocking traffic to those destinations. This is especially useful with sites such as Facebook that spread large amounts of IP space, but are constrained within a few net blocks.

Blocking Facebook

To find the most current list of Facebook subnets, query a server to find subnets for their AS and make an alias from there.

whois -h whois.radb.net -- '-i origin AS32934' | awk '/^route:/ {print $2;}' | sort | uniq

Once the list of netblocks is in hand, create an alias containing that data and then use it in Firewall rules to control direct access to Facebook.

Note that this doesn't account for using proxies or other anonymizing services that would allow users to access Facebook indirectly. (See below)

Using Squidguard

The SquidGuard package can be configured to block sites.

Prevent Bypassing of Blocking

With any of the above methods, there are still many ways to get around the defined blocks. The easiest and likely most prevalent is using any number of proxy websites. Finding and blocking all of these individually and keeping the list up to date is impossible. The best way to ensure these sites are not accessible is using content filtering capable of blocking by category.