Altering your computer's hosts file is the simplest way to protect your system from malware, viruses, porn, and offensive content. The host file is simply a table, like an excel spreadsheet of IP addresses, the backbone of the internet, and the domain name of the site, example.com.

Certain domains are known as spammers, adware, porn, and other truly offensive content. In the host file, those domains are redirected back to your own computer's IP address (127.0.0.1). This causes any web URL that directs to the offensive sites to never connect the "bad" sites, and a blank space is open in the browser window where the advertisement would have run.

It serves as an effective advertising filter as well. Most of the third-party banner ads and display ads are also "blank spaces" in the layout of the web page. No longer do you need to put up with advertising nonsense on every page that you visit. Much, though not all of it, will be eliminated with this hosts file fix.

"The computer file hosts is an operating system file that maps hostnames to IP addresses. It is a plain text file. Originally a file named HOSTS.TXT was manually maintained and made available via file sharing by Stanford Research Institute for the ARPANET membership, containing the hostnames and address of hosts as contributed for inclusion by member organizations. The Domain Name System, first described in 1983 and implemented in 1984,^[1] automated the publication process and provided instantaneous and dynamic hostname resolution in the rapidly growing network. In modern operating systems, the hosts file remains an alternative name resolution mechanism, configurable often as part of facilities such as the Name Service Switch as either the primary method or as a fallback method."

https://en.wikipedia.org/wiki/Hosts_(file)

We use a robust, crowd-sourced hosts file to filter the web experience for our users.  Someonewhocares.org provides an easy to use file for all operating systems,  Following the instructions on the site, we install the latest, most up-to-date filter to keep out the spam, advertisers. and malware.