Start by capturing the baseline before touching the UEFI lockdown: enumerate listening ports, review log settings, and note the network adapters. The point of the record is the second check, weeks later: without it, 'still locked down' is just an assumption.
1. Threat Model: What We Are Defending
Firmware is the first code that runs, and the last layer an attacker needs to keep working. The checks below live in the OS, verifying what the firmware actually does after your lockdown. You'll be root.
It captures the firmware build identity, the secure-boot state as the OS sees it, the services that boot with the firmware's blessing, and a lock on the kernel parameters the firmware hands to the boot process.
# The firmware build identity, as the OS sees it
systemctl list-units --type=service --state=running
# Tighten what new firmware-adjacent files default to
umask 0077
# Lock the kernel parameters the firmware hands over
sudo sysctl -w kernel.randomize_va_space=2
sudo sysctl -w kernel.sysrq=0
# What the platform reports about the USB stack at boot
udevadm monitor --environment --kernelMake the script executable and run it as root. Before any pipe into bash, take the time to read the whole thing. SELinux boxes deny the first pass - ausearch -m avc -ts recent shows which denial becomes your new allow rule.
2. Step-by-Step Configuration Log
Verification for UEFI/BIOS Security Hardening has to happen on the firmware and boot configuration, not in theory. Before you call the setup done, confirm boot order is locked to internal disk, Secure Boot is active with signed keys only, and BIOS/boot password protection is enabled and strong. The table below covers the most common failure modes in firmware hardening.
| Threat Vector | Impact | Remediation Action |
|---|---|---|
| Boot Order Tampering | External device boots before internal disk | Disable external boot and enforce boot order in BIOS |
| Secure Boot Bypass | Custom or unsigned bootloader accepted | Enable Secure Boot and confirm only signed boot entries are allowed |
| Password Weakness | BIOS password is short or trivially reset | Use strong BIOS password and confirm boot lock is active |
After the table, inspect firmware boot order and Secure Boot state, confirm external boot is disabled, and verify BIOS password protection is enabled with a strong credential.
| Threat Vector | Impact | Remediation Action |
|---|---|---|
| DNS Query Leaks | ISP collects every resolved name | Close plain port 53 and route queries via DoH/DoT. |
| IPv6 Bypass | Packets travel clear around the tunnel | Stop IPv6 at the interface level or give it the tunnel route. |
| Cleartext Handshakes | SNI leaks which service you reached | Enable ECH at every supporting destination. |
Close the loop: a WebRTC leak check in the browser you genuinely use, not a spare one. With a tunnel up, Firefox and LibreWolf still expose the local address through WebRTC; switch the surface off or lock it with a policy.
3. Verifying the Hardening Actually Holds
Ensure your operating systems and configuration parameters conform to the following standards:
- Verify Securing UEFI/BIOS: Firmware Hardening & Boot Protections survives a full reboot of the UEFI lockdown, not just the session you configured it in.
- Snapshot the working UEFI lockdown configuration now and prove the snapshot restores - an untested backup is a rumor.
- Strip out every unused UEFI lockdown feature; each one off is a door closed.
- Date-stamp each UEFI lockdown change in a plain log file so a future audit reads in minutes.
- Keep this UEFI lockdown workload away from any account that carries real identity or money.
- Verify the final UEFI lockdown state from a second, untouched device. The firmware you just locked will confirm the lock without objecting — treat any self-report as unproven until an outside check agrees.
Do not paste these commands and forget them; the day one fails, you will wish you had read them. Save the interface dump; it is the yardstick every later comparison needs. — diff it after any change and drift shows up fast. The resolver check is the proof that your chosen resolver - and not the network's - is actually answering. Functional and constrained are two different properties, and the command-line and sysctl flags are the only evidence of the second.
A practical warning on Securing UEFI/BIOS: Firmware Hardening & Boot Protections: the most common failure is applying settings on a live session and locking yourself out of that session. Always keep a second path in. If the box stops answering just after a change, revert the change before blaming the wiring. — not the network - roll back that piece before anything else.
Keep Securing UEFI/BIOS: Firmware Hardening & Boot Protections boring: documented, tested, and reversible. A UEFI lockdown setup that lasts is a documented one: write down what you changed and why, and delete any line whose purpose you cannot state out loud.
Real-world result of Securing UEFI/BIOS: Firmware Hardening & Boot Protections done halfway: a box that passes a quick test but fails the reboot. What relied on the old open setting will not recover on its own. Each step is only finished when the machine has restarted and the new state is confirmed on the live system — a saved setting that never took effect is worse than no setting at all.
Log the changes with dates, in the order they were made. Firmware and bootloader drift are quiet — the only way to catch it is to compare the live state against a record that predates it. Most drift is one line long, which is why the saved snapshot is worth the ten seconds it takes to compare.
One limit worth stating plainly: Securing UEFI/BIOS: Firmware Hardening & Boot Protections protects the machine and the link, not the person. A hardened machine does not protect an account whose identity is already known to the service. This closes real gaps, but it is a layer, not a system.
The reason Securing UEFI/BIOS: Firmware Hardening & Boot Protections is worth doing even partially: partial is still ahead of default. Most breaches exploit the gap between 'shipped' and 'hardened,' and closing even the obvious half removes the majority of easy wins for an attacker. Do not let perfect block done.
4. Rollback & Recovery Paths
We validated the full UEFI bench procedure against a current release before publishing; spot-check the outputs on your machine, because your configuration history will not match ours exactly.