This is obviously meant in sarcasm...do not leave your password on the default. Change it to ilovebitcoin like I do with all of my stuff!
The problem with changing the password is that you will forget it. An antminer should be root..root....a raspberry pi... pi...raspberry.. BAMT user...live
You would be floored to see how many of these I can find on the open internet....
In all seriousness, if you want to access ANYTHING you care about over the internet, please use a VPN appliance. Here's a cheap one: http://www.amazon.com/TP-LINK-TL-R600VPN-Gigabit-Broadband-Supports/
Poking holes in the firewall and port forwarding is a good way to open your network to attackers.