infra/config/network.nix

{
  networking.firewall.enable = true;

  services = {
    fail2ban = {
      enable = true;
      bantime-increment.enable = true;
    };
    openssh = {
      enable = true;
      openFirewall = true;
      settings = {
        KexAlgorithms = [
          "curve25519-sha256"
          "curve25519-sha256@libssh.org"
          "diffie-hellman-group16-sha512"
          "diffie-hellman-group18-sha512"
          "sntrup761x25519-sha512@openssh.com"
        ];
        PasswordAuthentication = false;
        PermitRootLogin = "prohibit-password";
        StreamLocalBindUnlink = "yes";
      };
    };
  };
}