Securing the VOS Telnet Daemon

Using SSH tunnels
� How users set up the SSH tunnel will depend on their SSH client
� What happens is
1. SSH client on the client host makes a connection to the SSH server
on the module (link A in next slide)
2. The SSH client on the client host starts listening on the port
specified (12345) during setup on the client host
3. The client’s telnet client makes a connection to localhost port 12345
(link B in next slide)
4. The SSH client sends this connection request to the SSH server on
the module which makes a connection to the port specified (23)
during setup on the client system (link C)
� The connections between the telnet client and SSH on the client
system and between SSHD and telnetd on the module are
unencrypted but never leave the local host
� Communication between hosts is encrypted by SSH
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