Editing Data remanence (section)

===Data on solid-state drives===

Research from the Center for Magnetic Recording and Research, University of California, San Diego has uncovered problems inherent in erasing data stored on [[solid-state drive]]s (SSDs). Researchers discovered three problems with file storage on SSDs:<ref name="SSD">{{cite journal|date=February 2011|title=Reliably Erasing Data From Flash-Based Solid State Drives|url=http://www.usenix.org/events/fast11/tech/full_papers/Wei.pdf|author1=Michael Wei|author2=Laura M. Grupp|author3=Frederick E. Spada|author4=Steven Swanson}}</ref>

{{quote|First, built-in commands are effective, but manufacturers sometimes implement them incorrectly. Second, overwriting the entire visible address space of an SSD twice is usually, but not always, sufficient to sanitize the drive. Third, none of the existing hard drive-oriented techniques for individual file sanitization are effective on SSDs.<ref name="SSD"/>{{rp|page=1}} |}}

Solid-state drives, which are flash-based, differ from hard-disk drives in two ways: first, in the way data is stored; and second, in the way the algorithms are used to manage and access that data. These differences can be exploited to recover previously erased data. SSDs maintain a layer of indirection between the logical addresses used by computer systems to access data and the internal addresses that identify physical storage. This layer of indirection hides idiosyncratic media interfaces and enhances SSD performance, reliability, and lifespan (see [[wear leveling]]), but it can also produce copies of the data that are invisible to the user and that a sophisticated attacker could recover. For sanitizing entire disks, sanitize commands built into the SSD hardware have been found to be effective when implemented correctly, and software-only techniques for sanitizing entire disks have been found to work most, but not all, of the time.<ref name="SSD"/>{{rp|section 5}} In testing, none of the software techniques were effective for sanitizing individual files. These included well-known algorithms such as the [[Gutmann method]], [[National Industrial Security Program|US DoD 5220.22-M]], RCMP TSSIT OPS-II, Schneier 7 Pass, and Secure Empty Trash on macOS (a feature included in versions OS X 10.3-10.9).<ref name="SSD"/>{{rp|section 5}}

The [[Trim (computing)|TRIM]] feature in many SSD devices, if properly implemented, will eventually erase data after it is deleted,<ref>{{Cite journal|last=Homaidi|first=Omar Al|date=2009|title=Data Remanence: Secure Deletion of Data in SSDs|url=https://www.diva-portal.org/smash/record.jsf?dswid=-8239&pid=diva2%3A832529|journal=}}</ref>{{citation needed|reason=This doesn't appear to be a secure method for deletion/sanitization|date=April 2017}} but the process can take some time, typically several minutes. Many older operating systems do not support this feature, and not all combinations of drives and operating systems work.<ref>{{cite web|url=http://forensic.belkasoft.com/en/why-ssd-destroy-court-evidence |title=Digital Evidence Extraction Software for Computer Forensic Investigations |publisher=Forensic.belkasoft.com |date=October 2012 |access-date=2014-04-01}}</ref>