Building Secure Servers with Linux

Chapter 4. Secure Remote Administration

Your server is bastionized, it resides in a firewall-protected DMZ network, and its services are fully patched and configured for optimal security. You’ve just installed it in a server room, which is monitored by surly armed guards and accessible only after peering into a retinal scanner and submitting to a body cavity search. Not that you plan to visit the system in person, though; it’ll be no problem to perform your administrative duties from the comfort of your office, thanks to good old Telnet.

What’s wrong with this picture?

Why It’s Time to Retire Clear-Text Admin Tools

TCP/IP network administration has never been simple. And yet, many of us remember a time when connecting a host to “the network” meant one’s local area network (LAN), which itself was unlikely to be connected to the Internet (originally the almost-exclusive domain of academia and the military) or any other external network.

Accordingly, the threat models that network and system administrators lived with were a little simpler than they are now: external threats were of much less concern then. Which is not to say that internal security is either simple or unimportant; it’s just that there’s generally less you can do about it.

In any event, in the old days we used telnet , rlogin , rsh , rcp , and the X Window System to administer our systems remotely, because of the aforementioned lesser threat model and because packet sniffers (which can be used to eavesdrop the passwords ...