NCSC Alert: Enable BitLocker PINs on Windows Laptops

The UK’s National Cyber Security Centre (NCSC) has published fresh guidance urging organisations to configure BitLocker with a pre-boot PIN on all Windows devices. The advice follows the discovery of a technique called YellowKey, which can bypass BitLocker protection when a device falls into the wrong hands.

What is BitLocker, and what has changed?

BitLocker is the encryption feature built into Windows that scrambles the data on a device’s hard drive. If a laptop is stolen, BitLocker should make the data unreadable to anyone who finds it.

Most organisations — and most IT systems by default — configure BitLocker to use the device’s Trusted Platform Module (TPM) chip alone. The TPM holds the encryption key and releases it automatically when the machine boots, so employees never have to enter a separate password to start their computer. Convenient, but, as YellowKey has demonstrated, not as safe as it sounds.

What is the YellowKey technique?

YellowKey exploits the Windows Recovery Environment (WinRE) — the built-in troubleshooting and repair tool that runs before Windows fully loads. Researchers showed that by manipulating WinRE, an attacker with physical access to a device can coax the TPM into releasing the BitLocker encryption key without needing any user credentials. In plain terms: a stolen laptop using TPM-only BitLocker could have its data exposed, even with encryption switched on.

Adding a pre-boot PIN changes the picture entirely. The TPM will only release the key if the correct PIN is entered before Windows starts — something an attacker cannot do without knowing it.

Why does this matter for your business?

Lost and stolen devices remain one of the most common ways small businesses lose sensitive data. A laptop left in a car, a bag grabbed at an airport, a device handed back by a departing employee — each of those scenarios could put client records, financial data, and confidential business files at risk.

Under UK GDPR, a data breach caused by an inadequately protected device can result in a regulatory investigation and significant fines. More immediately, it can mean notifying affected clients — a conversation no business owner wants to have.

The NCSC’s guidance makes clear that enabling a BitLocker PIN is a straightforward mitigation. It does not require expensive new hardware; it requires a policy change, ideally enforced through a device management platform such as Microsoft Intune or Group Policy.

What we are doing for managed clients

For clients on our managed IT support service, we review device encryption settings as part of our standard security baseline. Following the NCSC’s updated guidance, we are now auditing and rolling out BitLocker PIN policies across managed Windows estates where they are not already in place.

If you manage your own IT, here are the practical steps to take:

1. Check your current BitLocker configuration. Open a Command Prompt as administrator and run manage-bde -status to see which drives are encrypted and whether a PIN protector is active.
2. Enable a pre-boot PIN via Group Policy or Intune. The relevant setting is under Computer Configuration > Administrative Templates > Windows Components > BitLocker Drive Encryption > Operating System Drives > Require additional authentication at startup.
3. Set a strong PIN. The NCSC recommends at least six digits; longer is better. Consider using Windows Hello PIN, which can serve both login and BitLocker unlock, reducing friction for users who dislike extra steps.
4. Consider Network Unlock for office-based devices. If requiring a PIN on desktops that never leave the building is impractical, Network Unlock allows the PIN requirement to be bypassed automatically when the device is connected to your trusted office network.

Our cyber security services include device hardening and encryption policy reviews. If you are unsure whether your current setup meets the NCSC’s recommendations, we can carry out an assessment and make the necessary changes.

What about compliance and certification?

If your business holds Cyber Essentials or is working towards it, note that adequate encryption of portable devices is part of the scheme’s requirements. Getting BitLocker PINs right is a practical step towards both certification and demonstrable compliance with UK data protection law.

As a UKAS ISO/IEC 27001 certified organisation, we take device security seriously across our own estate and those of every client we support. This is not just a technical checkbox — it is one of the most effective things a business can do to limit the damage if a device is ever lost or stolen.

If you would like us to review your BitLocker configuration or roll out PIN policies across your Windows estate, get in touch or call 01452 701355 for a no-obligation chat.