{ config, lib, ... }: {

  boot = {
    tmp.useTmpfs = lib.mkDefault true;
    tmp.cleanOnBoot = lib.mkDefault (!config.boot.tmp.useTmpfs);

    # Disable kernel-param editing on boot
    loader.systemd-boot.editor = false;

    kernel.sysctl = {
      # Magic SysRq key -> allows performing low-level commands.
      "kernel.sysrq" = 0;

      ## TCP hardening
      # Prevent bogus ICMP errors from filling up logs.
      "net.ipv4.icmp_ignore_bogus_error_responses" = 1;
      # Reverse path filtering causes the kernel to do source validation of
      # packets received from all interfaces. This can mitigate IP spoofing.
      "net.ipv4.conf.default.rp_filter" = 1;
      "net.ipv4.conf.all.rp_filter" = 1;
      # Do not accept IP source route packets (we're not a router)
      "net.ipv4.conf.all.accept_source_route" = 0;
      "net.ipv6.conf.all.accept_source_route" = 0;
      # Don't send ICMP redirects (again, we're on a router)
      "net.ipv4.conf.all.send_redirects" = 0;
      "net.ipv4.conf.default.send_redirects" = 0;
      # Refuse ICMP redirects (MITM mitigations)
      "net.ipv4.conf.all.accept_redirects" = 0;
      "net.ipv4.conf.default.accept_redirects" = 0;
      "net.ipv4.conf.all.secure_redirects" = 0;
      "net.ipv4.conf.default.secure_redirects" = 0;
      "net.ipv6.conf.all.accept_redirects" = 0;
      "net.ipv6.conf.default.accept_redirects" = 0;
      # Protects against SYN flood attacks
      "net.ipv4.tcp_syncookies" = 1;
      # Incomplete protection again TIME-WAIT assassination
      "net.ipv4.tcp_rfc1337" = 1;

      ## TCP optimization
      # Enable TCP Fast Open for incoming and outgoing connections
      "net.ipv4.tcp_fastopen" = 3;
      # Bufferbloat mitigations + slight improvement in throughput & latency
      "net.ipv4.tcp_congestion_control" = "bbr";
      "net.core.default_qdisc" = "cake";
    };
    kernelModules = [ "tcp_bbr" ];
  };

  user.initialPassword = "nixos";
  users.users.root.initialPassword = "nixos";

  security = {
    # Prevent replacing the running kernel w/o reboot
    protectKernelImage = true;
    # So we don't have to do this later...
    acme.acceptTerms = true;
    # Allows unauthorized applications -> send unauthorization request
    polkit.enable = true;
  };
}
