A program to log into another computer over a network, to execute commands in a remote machine, and to move files from one machine to another. It provides strong authentication and secure communications over insecure channels. It is a replacement for rlogin, rsh (remote shell), rcp (remote file copy), and rdist (remote file distribution client program). When encryption is enabled, SSH protects a network from attacks such as IP spoofing, IP source routing and DNS spoofing. An attacker who has managed to take over a network can only force SSH to disconnect. The attacker cannot play back the traffic or hijack the connection when encryption is enabled.