What are the security implications when using SSH?
Using ssh is quite secure, but the security is only as good as the protection of ssh’s private keys. If an attacker can devise a way to run a shell as the BackupPC user then they will have access to BackupPC’s private ssh keys. They can then, in turn, ssh to any client machine as root (or whichever user you have configured BackupPC to use). This represents a serious compromise of your entire network. So in vulnerable networks, think carefully about how to protect the machine running BackupPC and how to prevent attackers from gaining shell access (as the BackupPC user) to the machine.
