NixOS must require the change of at least 50 percent of the total number of characters when passwords are changed.

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Verify NixOS enforces password complexity by requiring that at least 50 percent of the characters are changed with the following command:

$ grep difok /etc/security/pwquality.conf

difok=8

If the value of "difok" is set to less than "8", or is commented out, this is a finding.

Configure NixOS to enforce password complexity.

Add the following Nix code to the NixOS Configuration, usually located in /etc/nixos/configuration.nix or /etc/nixos/flake.nix:

environment.etc."/security/pwquality.conf".text = '' difok=8 '';

Rebuild and switch to the new NixOS configuration: $ sudo nixos-rebuild switch