Secure Shell (SSH) is a protocol that provides a secure connection to a router. Cisco IOS supports version 1 of SSH, which enables clients to make a secure and encrypted connection to a Cisco router. Before SSH was implemented, the only form of security available when accessing devices such as routers was Telnet username/password authentication, which is clearly visible with a network sniffer. Telnet is insecure because a protocol analyzer can view the information in clear text form. Figure 3-8 displays a simple protocol analyzer viewing information between a source address, 10.66.32.5, and the destination address 192.168.1.13 after a Telnet session is initiated by the address (PC) 192.168.1.13/24.