Provided is a method of remotely maintaining a computer system connected to a first private network of a first organization from a maintenance computer connected to a second private network of a second organization. The first and second private networks are connected to a public network and protected from the public network by respective first and second external firewalls. The first private network is separated from the computer system using a separation firewall configured to block network traffic that initiates at the computer system and is directed to the first private network. An isolation pipe is established that extends from the separation firewall over the first private network to the first external firewall, using virtual-private-network technology. A request to log into the computer system is transmitted from the maintenance computer through the isolation pipe to the computer system.