Avoid Debian Exploid using SSH

By | May 22, 2008

Not so long ago news surficed that the SSH protocol used in Debian was a lot less then secure. It appears that you can easily guess the key used for the encryption of all data send between the client and the server.

This would mean anyone could hack your debian server by just listening in to the communication between you and it. This is of course not what you want so here are a few easy steps to upgrade the faulty components.

  1. First you must update the apt by entering apt-get update
  2. After this it’s time to update the SSL libraries by entering apt-get install libssl0.9.8
  3. Know that the encryption is a lot more secure again its time to generate new keys for the server this can be done by executing the following line:
    ssh-keygen -N ” -t dsa -f /etc/ssh/ssh_host_dsa_key
  4. Also update the RSA key by entering:
    ssh-keygen -N ” -t rsa -f /etc/ssh/ssh_host_rsa_key
  5. Last but not least is restarting the SSH service to complete the update, this is done by running:
    /etc/init.d/ssh restart

Please note that after doing this and reconnecting you will most likely get a warning stating the server changed certificates. Which is true as you’ve done just that in the above steps.

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