Blocklists are a new feature of Guardian Firewall, introduced in version 2.0, allowing users to create custom groups of hostnames and IP addresses to block. These are blocked at a local level when connecting to Guardian by making use of a feature within iOS known as Proxy Auto Configuration. This feature allows us the ability to route specific connections to an intentionally unreachable destination, causing the connections to fail and ultimately helping you block more unwanted connections through Guardian Firewall.
When subscribed to Guardian Pro, you will additionally get access to Guardian-curated rule groups, allowing you to select experimental rule sets to empower you to control when and how your information may be accessed. This capability provides a more granular way to block known excessive tracking offenders.
Please keep in mind these experimental rule sets have not yet been thoroughly tested enough to add to our global server-side Blocklist. Some aggressive rule sets which will block certain types of content may adversely impact app or web functionality on your device. If these issues occur and interrupt your experience, please disable the specific rules to regain proper functionality.
More information about Proxy Auto Configuration can be found on Apple's developer pages here.