Use a firewall
Firewalls provide additional safety for devices connected to the internet. They block unauthorized access to your devices while still permitting outbound communication.
If setting your Obelisk up at home, check to see if your router has a firewall enabled. Most routers have firewall functionality built-in, but it may have to be enabled.
Most colocation facilities provide firewall protection as well. Check with your specific location to find out what types of security they have for devices in their care.