It's widely known that applications like telnet, rsh, and rlogin are vulnerable to attacks that can monitor or "sniff" network traffic and obtain login passwords or other data sent over unencrypted connections. Protocols like SSH have been assumed to be safe even if an attack does monitor network traffic, because the transmitted data is encrypted.
Unfortunately, this is no longer the case, according to an advisory that was sent out by the Openwall Project and that discusses weaknesses in the SSH-1 and SSH-2 protocols. Although attackers may not be able to "read" transmitted data sent in a Secure Shell session, it's possible that they could guess the length of passwords and shell commands. The captured data could be used to try brute-force attacks on passwords. It should be noted, however, that it is still preferable to utilize encrypted protocols.
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