Dear all, I have searched across Google for a while to try and understand the security impact of certain changes in our sshd_config file, but because I could not find the answer, I decided to post here. I hope that here is the right place. A developer uses SSH to connect to servers in his application, but it cannot connect. The Dev has shown that if I change the these settings in the sshd_config :- From: # To disable tunneled clear text passwords, change to no here! PasswordAuthentication no # Change to no to disable s/key passwords #ChallengeResponseAuthentication yes To: ChallengeResponseAuthentication no #PasswordAuthentication ... (second one commented out, so the default setting is used) I have tried to understand what the impact is for security and other varibles across our systems, but cannot. We use RSA and DSA keys to connect between servers, and UNIX password authentication. Some keys have passphases, and others do not. Servers are SLES, Opensuse, Debian and HPUX. Can anyone think of any, or even point me to a URL that could explain these in near-layman's terminology as I am not an SSH expert? Yours sincerely, J.