By prefixing the URL of an endpoint with icmp://, you can monitor a given target using ICMP.

For instance, setting icmp://example.org will cause Gatus to ping the underlying hostname and resolve the placeholder [CONNECTED] to true or false based on whether a connection was successfully established or not.

While this is mostly useful to check if a host is alive, using it for its opposite effect can be beneficial to ensure hosts that shouldn't be reachable remain unreachable.