Erasing Hidden Disk Areas: Critical for Compliance
Learn the importance of erasing hidden disk areas like HPA, DCO, DFA, and remapped sectors to ensure data security and meet data protection requirements.
Privileged access controls, encrypted storage media, and multi-factor authentication provide a sense of relief about the security of onsite data storage systems. However, when these systems need upgrading or have reached end of life, they must be erased securely — including wiping hidden disk areas.
Most often, risks posed by remnant and hidden data are overlooked. NIST SP 800-88 Rev 1 Guidelines for Media Sanitization highlight that residual data fragments can pose significant security risks, especially on IT assets leaving organizational premises.
Why Complete Sanitization Matters
Whether it's a periodic hardware refresh, end-of-life asset disposal, or CSR laptop donations — no data-bearing IT asset should leave organizational control without complete media sanitization. Partial erasure or leaving data in hidden sectors can cause data breaches, as user data remnants can reveal sensitive information.
Understanding Hidden Disk Areas
Hidden areas and remapped sectors may contain various data types including authentication details, deleted data fragments, backup copies, system logs, metadata, and firmware recovery information. Although these areas exist on the disk, they are not accessible by users, the operating system, BIOS, or UEFI.
HPA (Host Protected Area)
Present on HDDs and SSDs, introduced by ATA-4 standard. This reserved area stores diagnostic utility functions and enables system boot when normal boot processes fail.
DCO (Device Configuration Overlay)
Provides PC vendors the option to customize available storage on a disk. By configuring the same number of sectors in different-sized drives, DCO makes the OS see drives as the same size.
DFA (Disk Firmware Area)
Also known as the Service Area, DFA remaps sectors identified as "bad" or "failed" to new addresses. This zone also contains elements enabling advanced disk security.
Why Hidden Data Poses Serious Risks
Hidden areas on a disk are not accessible by standard file system commands, BIOS, Operating System, or users. Specialized ATA commands or tools are required to access HPA and DCO — which means data can be written to these areas, making them vulnerable to leakage.
Research Finding
"It is possible to create an HPA that is approximately the same size as the HDD. This means the HPA, DCO, or combined can potentially store large amounts of information, invisible to investigators and analysis tools."
— International Journal of Digital Evidence
Data recovery and forensic tools like PC-3000 can retrieve data from hidden zones. Leaving any scope of data recovery jeopardizes the security of confidential organizational information.
Compliance Standards Requirements
If an organization claims to have erased data from IT assets as per NIST or IEEE guidelines, hidden zones must also be erased. This is critical and cannot be overlooked — non-compliance can result in incomplete erasure, violating data protection laws that mandate complete sanitization.
NIST Clear
Removes data from user-addressable areas only. NIST explicitly notifies about remnant data possibly remaining on disk.
Not suitable for hidden areas
NIST Purge
Recommended for erasing data from entire storage media, including HPA, DCO, and remapped sectors.
Complete sanitization
NIST Purge Methods for HDDs
ATA Sanitize Device
- • Overwrite EXT command
- • Cryptographic Erase (CRYPTO SCRAMBLE EXT)
SECURE ERASE UNIT
Standard secure erase command for complete drive sanitization
TCG Cryptographic Erase
Through Trusted Computing Group Opal SSC or Enterprise SSC
NIST Purge Methods for SSDs
Block Erase
Sanitize command for flash storage
Cryptographic Erase
CRYPTO SCRAMBLE EXT command
TCG SSC
Enterprise-grade cryptographic erase
IEEE Purge Techniques for ATA Devices
- Cryptographic Erase
- Sanitize Block Erase
- Sanitize Overwrite
- SECURITY ERASE UNIT (Enhanced Erase Mode)
The D-Secure Solution
Executing these techniques through OEM-provided methods requires advanced technical knowledge. Manually performing them on each device is not feasible — too time-consuming and resource-intensive for bulk wiping.
Organizations should use enterprise-grade software like D-Secure Drive Eraser that supports complete media sanitization including hidden disk areas. The software uses methods like NIST 800-88Clear and Purge to completely erase data — including hidden zones (HPAs, DCOs, DFAs) and remapped sectors. D-Secure Drive Verifier can then verify the erasure outcome and ensure no data traces remain.
Solutions for Security
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How Do Experts Handle This?
Standard Compliance
Meeting NIST 800-88 and GDPR standards with full audit trails.
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