Last updated: March 2026
Why BitLocker isn’t a silver bullet and the problems it can cause if you’re not prepared
Encryption is everywhere these days — and for good reason. BitLocker can protect your Windows systems and data at rest, helping you meet compliance requirements and keep data secure even if drives are lost or stolen. But like any technology, it comes with pros and cons — and the BitLocker problems that tend to catch people off guard show up in backups, recovery, and everyday production operations.
Over the years, we have seen a range of issues that clients faced that were directly related to having BitLocker enabled. These range from a mild annoyance to complete backup failure, particularly with Hyper-V systems.
Before you roll out BitLocker across your environment, it is worth stepping back and making sure you truly understand what it does — and why that could cause problems in the context of backups, recovery, and system maintenance.
Here are 6 side effects to understand before turning on BitLocker.
TL;DR
BitLocker is excellent at protecting data at rest, but it can cause problems with system workflows, backups, and recovery in ways that are not obvious. If you do not account for these factors ahead of time, you could end up with longer outages, failed backups, or unexpected technical issues.
What BitLocker does and doesn’t do
At a high level, BitLocker encrypts drives so that if your hardware is stolen, the data cannot be accessed. That is its core purpose, and it does this well.
But BitLocker does not:
- Eliminate the need for good backups
- Protect systems while they are running (for example, in memory or during live operations)
- Automatically work with every backup method, snapshot mechanism, or recovery environment
Understanding these gaps upfront will save a lot of pain later.
Known problems and side effects of BitLocker
1. BitLocker can stop your systems from booting after a Windows update
This issue has nothing to do with your backup software and can happen on any normal working day in production. BitLocker ties the ability to boot Windows to a set of measured values stored in the TPM — things like firmware state, boot files, and Secure Boot configuration. When something changes those measurements, such as a routine Windows or firmware update, BitLocker treats it as a potential tampering attempt and refuses to start. Instead of booting into Windows, the machine stops at a blue screen demanding the 48-digit recovery key. Until that key is entered, the system will not start.
This is not a theoretical risk. In October 2025, Microsoft’s routine monthly security update caused exactly this — a significant number of machines stopped at the BitLocker recovery screen after the update installed, and in many cases the recovery environment also refused to accept USB keyboard input, leaving administrators unable to even type the recovery key. Microsoft had to release an emergency out-of-band patch to resolve it. Read more about the October 2025 incident →
This means you should:
- Store recovery keys centrally and securely
- Plan for firmware and WinRE updates that may trigger recovery mode, and make sure decryption keys are on hand if needed
- When creating BackupAssist bootable media, use an installation disk rather than the built-in version of Windows
2. BitLocker can break your backups
One of the most serious problems we see is with backups — particularly when it comes to Volume Shadow Copy Service (VSS) based backups or snapshots on encrypted volumes. When BackupAssist takes a backup of an encrypted drive, it creates a virtual hard disk (.VHDX) copy of your disk. That VHDX file, along with the VSS snapshot — which is also a mounted clone of your drive — is encrypted with BitLocker. In some cases, that means the data may not be accessible.
In certain environments, such as domain controllers with BitLocker-encrypted system partitions:
- If you are backing up at the host level (which is the recommended approach with BackupAssist), your domain controller guest may not back up correctly. The NTDS volume for your Active Directory snapshot cannot be read at the host level, leaving the Active Directory portion of the guest unprotected.
- Performing a granular file restore from inside any guest encrypted with BitLocker requires the mounted backup file to be manually unlocked through Windows before the BackupAssist restore console can access it.
This behaviour is documented by Microsoft and is by design, not a bug. See Microsoft’s official documentation on this known issue →
How to work around this:
- Consider encrypting only data drives for Active Directory guest servers, or back up at the guest level for these systems rather than the host
- Evaluate whether the guests need to be encrypted, or whether the host volumes where the guest VHDX files are stored should be encrypted instead
- Test backups and restores after enabling BitLocker — do not assume they will just work
3. Hardware changes can leave your data permanently inaccessible
BitLocker works best with a TPM (Trusted Platform Module) and UEFI firmware. When restoring to new hardware, deployments can fail or require fallback to USB keys or passwords. Firmware updates, BIOS changes, and boot order adjustments can also trigger recovery mode.
This came up recently in a real situation I handled: a PC was temporarily encrypted with BitLocker for testing, but the motherboard failed before the drive could be decrypted. Connecting that drive to a new system caused it to lock down completely — it would only accept the encryption key, not the password. This happens because BitLocker ties decryption to the TPM chip on the original motherboard. A replacement board has a fresh TPM with no knowledge of the existing encryption. Microsoft’s BitLocker recovery documentation covers this scenario in detail →
BitLocker has hardware dependencies worth planning for:
- TPM must be enabled and provisioned correctly
- Firmware changes may cause lockdown and require recovery keys
- Boot partition layout must meet BitLocker’s requirements
These are not edge cases — they are predictable consequences of how BitLocker works, and they need to be planned for.
4. Poor key management will lock you out permanently
Centralized key management is essential. Without it:
- Recovery keys can be lost
- Systems may enter recovery mode with no straightforward way to unlock them
- Helpdesk teams end up spending time tracking down keys
Best practice is to store recovery keys centrally before enabling BitLocker — for example, in Active Directory, Intune, or Azure AD. Failing to do this is one of the most common operational mistakes we see.
5. Degraded performance can be expected
Encryption comes at a performance cost. On older or heavily loaded systems, BitLocker can introduce noticeable performance overhead — especially during the initial encryption process. Progress indicators during encryption are often unclear, making it difficult to gauge how long tasks will take.
The practical consequences are:
- Expect slower performance on older hardware
- Plan encryption windows around production schedules
- Communicate with users and plan timing appropriately
6. BitLocker gives a false sense of security if misunderstood
BitLocker protects data at rest. That is its job. It does not protect against:
- In-memory attacks
- Cold boot attacks
- Malware running on an active system
In other words, BitLocker is not a replacement for:
- Good endpoint protection
- Patch management
- Network security controls
- Backup and recovery planning
Encryption is a valuable piece of the puzzle — but not the whole picture.
Summing it up
BitLocker is a powerful tool. But like any tool, it comes with tradeoffs that matter when you are planning backups and disaster recovery.
Before you roll out BitLocker:
- Understand how recovery scenarios work
- Test backups after encryption
- Make sure recovery keys are safely stored
- Plan for hardware and firmware quirks
- Do not rely on encryption alone to protect against all failure modes
BitLocker will secure your data at rest — but it will not replace good backup practices, thoughtful planning, or tested disaster recovery procedures.
Understanding these side effects upfront can be the difference between a smooth deployment and a crisis at the worst possible time.
