This article covers AdGuard for Mac, a multifunctional ad blocker that protects your device at the system level. To see how it works, download the AdGuard app
During the Installation of AdGuard on macOS High Sierra (or later versions) you may see a message: "System Extension Blocked". This is a new security mechanism that appeared in High Sierra, it requires you to explicitly allow the installation of a third-party system extension. To complete the installation of AdGuard you have to manually allow loading the extension in System Preferences → Security & Privacy → General.
Click the "Allow" button, and after that you will be able to proceed with the installation as normal.