Secure Erase
Decommissioning is the policies and procedures that govern the removal of devices and software from production networks, and their subsequent disposal through sale, donation, or as waste.
- if asset is disposed of by resale, gift, or recycling, there is a risk that:
- software licenses could be misused
- or configuration information valuable to an attacker could be leaked
- risks mitigated by invoking the built-in factory reset
- wipes any custom configuration settings
- factory reset may leave data remnants
- data remnant removal refers to ensuring that no data is recoverable from assets
- critical to prevent confidential data being compromised
- do so by:
- destroying the media
- sanitizing it
- removing confidential information but leaving media intact for reuse
- sanitizing and HDD is called overwriting
- performed using the drive’s firmware tools, or a utility program
- basic type is called zero filling
- sets each bit to zero
- single-pass zero filling can leave patterns that can be read with specialist tools
- more secure method is:
- overwrite with one pass of all zeros
- then pass of all ones
- then 1 or more passes in a pseudorandom pattern
- data remnant removal refers to ensuring that no data is recoverable from assets
Secure Erase
SATA and Serial Attached SCSI (SAS) specifications include a Secure Erase (SE) command.
- since 2001
- invoked using a drive/array utility or the hdparm Linux utility
- on HDDs, performs a single pass of zero filling
- for SSDs, hybrid drives, and some USB flash drives,
- overwriting methods are not reliable
- devices use wear-leveling routines in the drive controller to communicate which locations are available for use to any software process accessing the device
- overwriting methods are not reliable
- on SSDs SE command marks all blocks as empty
- block is the smallest unit on flash media that can be given an erase command
- firmware’s automatic garbage collectors then perform the actual erase of each block over time
- if process is not completed, there is a risk of remnant recovery
- requires removing the chips from the device to analyze in specialist hardware
Instant Secure Erase
- HDDs and SSDs that are self-encrypting drives (SEDs) support a crypto erase
- invoke a SANITIZE command set in SATA and SAS standards
- from 2012
- implemented as Instant Secure Erase (ISE)
- with an SED, all data on the drive is encrypted using a media encryption key (MEK)
- when erase command is issued, the MEK is erased
- renders data unrecoverable
- invoke a SANITIZE command set in SATA and SAS standards