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Guide to the Secure Configuration of Debian 11

Rules, Groups, and Values defined within the XCCDF Benchmark

  • Verify Permissions on SSH Server Private *_key Key Files

    SSH server private keys - files that match the <code>/etc/ssh/*_key</code> glob, have to have restricted permissions. If those files are owned by t...
    Rule Medium Severity
  • Verify Permissions on SSH Server Public *.pub Key Files

    To properly set the permissions of /etc/ssh/*.pub, run the command:
    $ sudo chmod 0644 /etc/ssh/*.pub
    Rule Medium Severity
  • Remove SSH Server iptables Firewall exception (Unusual)

    By default, inbound connections to SSH's port are allowed. If the SSH server is not being used, this exception should be removed from the firewall ...
    Rule Unknown Severity
  • Configure OpenSSH Client if Necessary

    The following configuration changes apply to the SSH client. They can improve security parameters relwevant to the client user, e.g. increasing ent...
    Group
  • Configure OpenSSH Server if Necessary

    If the system needs to act as an SSH server, then certain changes should be made to the OpenSSH daemon configuration file <code>/etc/ssh/sshd_confi...
    Group
  • SSH RekeyLimit - size

    Specify the size component of the rekey limit.
    Value
  • SSH RekeyLimit - size

    Specify the size component of the rekey limit.
    Value
  • SSH Compression Setting

    Specify the compression setting for SSH connections.
    Value
  • SSH Privilege Separation Setting

    Specify whether and how sshd separates privileges when handling incoming network connections.
    Value
  • SSH LoginGraceTime setting

    Configure parameters for how long the servers stays connected before the user has successfully logged in
    Value
  • SSH MaxStartups setting

    Configure parameters for maximum concurrent unauthenticated connections to the SSH daemon.
    Value
  • Set SSH Client Alive Count Max to zero

    The SSH server sends at most <code>ClientAliveCountMax</code> messages during a SSH session and waits for a response from the SSH client. The optio...
    Rule Medium Severity
  • Set SSH Client Alive Count Max

    The SSH server sends at most <code>ClientAliveCountMax</code> messages during a SSH session and waits for a response from the SSH client. The optio...
    Rule Medium Severity
  • Set SSH Client Alive Interval

    SSH allows administrators to set a network responsiveness timeout interval. After this interval has passed, the unresponsive client will be automat...
    Rule Medium Severity
  • Disable Host-Based Authentication

    SSH's cryptographic host-based authentication is more secure than <code>.rhosts</code> authentication. However, it is not recommended that hosts un...
    Rule Medium Severity
  • Allow Only SSH Protocol 2

    Only SSH protocol version 2 connections should be permitted. The default setting in <code>/etc/ssh/sshd_config</code> is correct, and can be verifi...
    Rule High Severity
  • Disable Compression Or Set Compression to delayed

    Compression is useful for slow network connections over long distances but can cause performance issues on local LANs. If use of compression is req...
    Rule Medium Severity
  • Disable SSH Access via Empty Passwords

    Disallow SSH login with empty passwords. The default SSH configuration disables logins with empty passwords. The appropriate configuration is used ...
    Rule High Severity
  • Disable GSSAPI Authentication

    Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms like GSSAPI. <br> The default SSH configuration disallows ...
    Rule Medium Severity
  • Disable Kerberos Authentication

    Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms like Kerberos. <br> The default SSH configuration disallow...
    Rule Medium Severity

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