Access Rules are a ruleset within NG Firewall to allow or block traffic specifically destined to the NG Firewall itself. They are located at Config > Network > Advanced > Access Rules.
We discourage the creation of rules here as they can be a huge security risk, specifically if the NG Firewall is your gateway device. The default rules cannot be modified in any way, and we encourage users to disable Allowing SSH & Allowing HTTPS on WANs for tighter security.
However, there are some scenarios where it may be necessary to create rule(s) to allow traffic to the NG Firewall , such as with remote SMTP servers. In these cases, we highly recommend configuring the rules to be as strict as possible, which would include adding a condition such as Source Address which will not allow anything other than the specific network, and specifying only the remote network that needs to access the NGFW via that protocol.