DNS filtering is a network security mechanism that controls and blocks access to websites or services based on their domain names. It operates by intercepting DNS queries from devices within a network, and either allowing or blocking these queries based on predefined security policies or blacklists. This method is effective in preventing access to malicious, inappropriate, or unapproved websites, enhancing overall network security and compliance. DNS filtering is also utilised to enforce content restrictions in various environments like schools and workplaces.