Introduction

SSH stands for "Secure SHell." SSH is a replacement for telnet, rsh, and rlogin, to allow secure shell access to remote machines over an untrusted network. Telnet was designed at a time when the Internet consisted of a relatively small number of universities, and no one had ever heard of a packet sniffer. Packet sniffers such as sniffit and tcpdump are now relatively common - they have some highly practical uses, but obviously can also be used to collect passwords of those using unencrypted connections on a local network. Even if the password handshaking is encrypted, quite a bit of personal information can be collected watching an unencrypted transaction after the passwords. SSH packets looks like garbage to a packet sniffer.