I would like to add security (e.g. a login with a password) for the public-ip for my Azure VM. Because else everybody could e.g. deploy smart contracts via the cakeshop links or turn off and on the Ethereum nodes.
Does anybody know how to do it?
On
There is no such thing as a password for a public IP, a public IP is just a resource assigning IP's to a network interface, nothing more.
If you are hosting an application in Azure it is up to you to make sure this is secure. Ideally, this would be done through authentication at the application layer, to prevent users from being able to do anything in the application without authenticating. If your application does not provide this then you may want to take a closer look at your application and whether it is fit for purpose.
If application level authentication is not possible then you could look at adding authentication at the application server level, be this Apache, IIS, Tomcat etc. You would need to look at the appropriate documentation for your application server.
It seems that you cannot set a password for the public IP. But you can set the password for the VM. For the security of the VM, you can use the Azure Network Security Group to filter the traffic. For more details, see Filter network traffic with a network security group.
For more security to the VM, you can try the Identity of Azure AD. Take a look at this Configure managed identities for Azure resources on a VM. Hope this will help you.