Problem
How to connect to your server's KVM unit if you get the error message "this application was blocked by your Java security settings"
tl;dr
Control Panel -> Java -> Security tab -> Edit site list -> add the KVM IP.
Solution
A KVM unit, or Keyboard-Video-Mouse, is a remote management box that allows you to remotely connect to a PC (typically, a server) and input commands at a hardware level. More technically, it's a relay for keyboard and mouse input to the server, and monitor output from your server. It is most commonly used for installation and troubleshooting of a remote system, such as when its network settings are unavailable, or changes have to be made at the BIOS/bootloader level - before you can actually login via SSH or RDP.
Your server may come with a built-in KVM unit, either in the form of an Intel Remote Management Moduel (RMM), or IPMI. Alternatively, you may ask us to hook up a KVM to your server at any time. Either way, you need to know the KVM's IP address and login credentials (username/password).
Access the KVM
You can access the KVM through your web browser by typing in its IP address:
111.222.33.44
The browser will usually interpret it along the lines of:
https://111.222.33.44/auth.asp
You get a similar prompt in your browsers's Window (this example is for Chrome):
Your connection is not private
Attackers might be trying to steal your information from 111.222.33.44 (for example, passwords, messages, or credit cards).
Advanced [Back to Safety]
Click on Advanced and then on Proceed to 111.222.33.44 (unsafe). Enter your provided login credentials, which will take you to the KVM console. Go to Remote Control, Remote Console, or some version thereof (the name is different depending on the specific KVM unit).
Unblock the Application
Now, here is the typically most confusing part: the KVM remote console is a self-signed Java applet. However, as of the most recent security update, Java blocks all self-signed applications from executing. To run it, you need to add an exception to your Java Control Panel. To do so, go to:
Control Panel -> Java -> Security -> Edit Site List
Then add your KVM IP:
https://111.222.33.44
Press OK, and you should be able to open the KVM remote panel. Press "Yes" or "Allow" to any Java security prompts.
- Updated