Abstract: A computer system comprises first and second networks, the second network being protected by a firewall. The first network includes a first terminal server, which is granted permission to access the second network through the firewall. The second network includes a second terminal server, including a number of application programs that can be run remotely. A user on the first network who has successfully logged on to the first terminal server is then enabled to log on to the second terminal server through the first terminal server, and may then remotely run application programs in the second server. The invention finds particularly application in enabling support staff to access multiple networks, to enable them to diagnose and fix problems.