Why Erasing Hidden Disk Areas Is Crucial for Compliance?
Data erasure isn’t truly complete unless hidden and inaccessible areas of a disk are also wiped clean. According to industry standards like NIST SP 800-88 Rev 1 and IEEE 2883-2022, proper media sanitization must include the permanent removal of data from locations such as the Device Configuration Overlay (DCO), Host Protected Area (HPA), and remapped sectors. If these regions are ignored, sensitive data can still be recovered using forensic tools putting organizations at serious risk of non-compliance with data protection laws. In this article, we explore why erasing hidden disk areas is essential, the potential compliance threats posed by residual data, and the most effective methods for ensuring complete and irreversible data sanitization.
While privileged access controls, encrypted storage, and multi-factor authentication can offer a sense of security, they don’t eliminate the need for proper data sanitization especially when IT systems are upgraded or reach end-of-life. At that point, secure erasure becomes essential, including wiping hidden disk areas that are often overlooked. Residual data left in areas like remapped sectors or hidden partitions poses a real risk, as emphasized in NIST SP 800-88 Rev 1, which outlines best practices for media sanitization to prevent data leakage when devices leave an organization’s control.
The reasons for decommissioning IT assets may vary from routine hardware refresh cycles and disposing of obsolete systems to donating desktops and laptops as part of CSR initiatives. Regardless of the reason, no data-bearing device should leave the organization without complete and verifiable sanitization. Even within the organization, when systems are repurposed for instance, moving a laptop from R&D to accounting sanitization ensures data separation, security, and compliance with Green IT policies.
To avoid the risk of data breaches from hidden or inaccessible disk areas, organizations must use a certified data sanitization tool capable of detecting and securely erasing data from all storage regions, including the Host Device Configuration Overlay (DCO), Host Protected Area (HPA), and remapped sectors. Only then can data confidentiality be truly guaranteed.
What Are Hidden Areas on a Drive and What Kind of Data Do They Hold?
Hidden areas and remapped sectors on storage drives can quietly store a wide range of sensitive information authentication credentials, deleted file fragments, backup copies, system logs, metadata, and even firmware or recovery data. Although this data resides on the drive, it remains inaccessible to users, the operating system, and even to low-level system tools like BIOS or UEFI.
On ATA and IDE drives, these hidden zones typically include:
- HPA (Host Protected Area): Found on both HDDs and SSDs, HPA was introduced under the ATA-4 standard. It reserves space on the disk for diagnostic tools and emergency boot functions if the primary boot path fails.
- DCO (Device Configuration Overlay): This area allows OEMs or system integrators to standardize disk capacity across different brands and models by masking part of the drive. As a result, the OS sees all drives as the same size, regardless of their true capacity.
- DFA (Disk Firmware Area) / Service Area: DFA handles remapped sectors parts of the disk identified as “bad” or unreadable. The firmware assigns these blocks new addresses, making them invisible to the OS. This zone also contains low-level utilities and security features used by the disk firmware itself.
In many modern storage devices, Accessible Max Address (AMA) replaces or works in conjunction with these legacy zones, continuing the practice of hiding critical areas from user-level access.
Understanding and securely erasing these regions is vital for complete data sanitization and compliance with standards like NIST SP 800-88 Rev 1.
Why Hidden Disk Areas Pose Serious Data Security Risks?
Hidden zones on a storage drive such as the Host Protected Area (HPA) and Device Configuration Overlay (DCO) aren’t accessible through typical operating system commands, BIOS, or even advanced file system tools. Instead, they require specialized ATA commands or forensic utilities to read or modify. This makes them particularly dangerous when it comes to data leakage and compliance risks.
In fact, studies like the one published in the International Journal of Digital Evidence have confirmed just how serious this risk is. The research notes that it’s technically possible to create an HPA nearly as large as the hard drive itself, making it capable of storing significant volumes of hidden data. Such data can easily bypass routine erasure processes and remain invisible to investigators and standard data analysis tools.
Advanced recovery tools, such as PC-3000, can extract information from these hidden sectors, which poses a direct threat to the confidentiality and integrity of organizational data. If sensitive files, credentials, or proprietary content remain recoverable, it could lead to data breaches, compliance violations, or even legal consequences.
Therefore, if an organization claims to follow data sanitization standards like NIST SP 800-88 Rev 1 or IEEE 2883-2022, it’s essential that these hidden areas are included in the wipe process. Overlooking HPA, DCO, or remapped sectors means the data destruction process is incomplete which could result in non-compliance with global data protection laws such as GDPR, HIPAA, or CCPA.
To ensure true data sanitization, organizations must use certified tools that are capable of detecting and erasing data in hidden disk areas, eliminating every potential trace.
Techniques to Erase HPA and DCO for Complete Data Sanitization
While most modern hard drives particularly ATA-based HDDs and SSDs include hidden areas like HPA (Host Protected Area) and DCO (Device Configuration Overlay), these zones are not automatically wiped during standard data erasure processes.
According to NIST SP 800-88 Rev 1 and IEEE Std 2883-2022, it’s essential to reset any disk configuration that may block access to these hidden areas before initiating sanitization. This ensures that areas such as HPA, DCO, and AMA (Accessible Max Address) are fully exposed and can be securely erased. After sanitization, it’s strongly recommended to verify the process using trusted validation tools to confirm that no data remnants remain.
It’s important to understand that different sanitization methods handle hidden areas differently:
- NIST “Clear” only targets user-addressable areas of the disk, which means HPA, DCO, and remapped sectors can be left untouched. Even NIST highlights the risk of residual data using this method.
- Similarly, the IEEE Clear method is not recommended for sensitive data, especially when erasing non-addressable zones is necessary.
To ensure the complete removal of all data, including hidden and remapped sectors, the “Purge” method is the recommended approach under both NIST and IEEE guidelines.
Using NIST Purge techniques provides a more secure and thorough erasure process that covers:
- All visible and hidden areas of the disk
- Non-addressable sectors, including HPA and DCO
- Remapped sectors and firmware-level storage regions
These methods are essential when dealing with classified, regulated, or high-sensitivity data, especially prior to decommissioning or repurposing any IT asset.
Purge Techniques to Wipe Hidden Disk Areas on HDDs and SSDs
To ensure full sanitization of storage devices including hidden zones like HPA, DCO, and remapped sectors ATA hard drives (HDDs) and solid-state drives (SSDs) require specific commands under the IEEE Purge guidelines. The methods vary based on the device type and its supported features.
For HDDs, the following options are available:
Depending on the drive’s compatibility, one of these ATA Sanitize Device features can be applied:
- Overwrite EXT Command – Overwrites the user-addressable and hidden areas with random or fixed data.
- Cryptographic Erase (CRYPTO SCRAMBLE EXT) – Destroys the encryption key, rendering data irretrievable.
- SECURE ERASE UNIT Command – A command to erase all data using standard or enhanced secure erase modes.
- Cryptographic Erase via TCG SSC or Enterprise SSC – Erasure performed via security standards from the Trusted Computing Group (TCG).
For SSDs, the supported options include:
- Sanitize Block Erase Command – Erases memory blocks at the flash level.
- Cryptographic Erase (CRYPTO SCRAMBLE EXT) – Deletes encryption keys, making stored data unreadable.
- Cryptographic Erase via TCG SSC or Enterprise SSC – Secure erasure via TCG-compliant controllers.
IEEE Purge Methods for ATA Devices
To comply with the IEEE Purge standard, one of the following operations can be used to fully sanitize ATA drives:
- Cryptographic Erase
- Sanitize Block Erase
- Sanitize Overwrite
- SECURITY ERASE UNIT (Enhanced Erase Mode)
Why Automation is Critical for Large-Scale Wiping
Although these techniques are effective, executing them manually across multiple devices is time-consuming, resource-intensive, and requires advanced technical skills. This makes manual erasure impractical for organizations needing to sanitize data at scale.
Instead, organizations should turn to certified solutions like CubexSoft Drive Eraser, which automates the entire sanitization process. The tool supports industry-standard NIST 800-88 Clear and Purge methods, ensuring complete erasure of data including from hidden zones like HPA, DCO, DFA, and remapped sectors.
