Can I restrict access to my cluster via a firewall?

Yes, for dedicated instances.

A firewall lets you restrict access to your cluster so that only your servers will have access. You can also set up different ports for different ranges, so, for example, your servers can access port 5762 (AMQP), but the management interface is still open to all.

Configure a firewall for your cluster directly from our UI. You can specify an IP range and decide which ports that should be opened for that range. All other ports to your instance will be closed.