Editing SD card (section)

===Counterfeits===
[[File:Samsung Pro 64gb micro-SDXC original and falsification front and back.jpg|thumb|[[Samsung Electronics|Samsung]] Pro 64&nbsp;GB microSDXC original (left) and counterfeit (right): The counterfeit claims to have 64&nbsp;GB in capacity, but only 8&nbsp;GB (Class 4 speed) are usable: When trying to write more than 8&nbsp;GB, [[data loss]] occurs. Also used for [[SanDisk]] 64&nbsp;GB fakes.]]
[[File:Decapsulated microSD memory card lineup-genuine, questionable, and fake-counterfeit.jpg|thumb|Images of genuine, questionable and counterfeit microSD (Secure Digital) cards before and after decapsulation. Details [http://www.bunniestudios.com/blog/?page_id=1022 at source], photo by [[Andrew Huang (hacker)|Andrew Huang]]]]

Commonly found on the market are mislabeled or counterfeit Secure Digital cards that report a fake capacity or run slower than labeled.<ref>{{cite web |last=bunnie |title=On MicroSD Problems |url=https://www.bunniestudios.com/blog/?page_id=1022 |access-date=2024-01-22 |website=bunniestudios.com |archive-date=2024-09-11 |archive-url=https://web.archive.org/web/20240911013533/https://www.bunniestudios.com/blog/on-microsd-problems/ |url-status=live }}</ref><ref name="c't2007">{{cite web |last=Schnurer |first=Georg |title=Gefälschte SD-Karten |language=de |trans-title=Fake SD-cards |publisher=Heise mobile – c't magazin für computertechnik |date=2007-02-28 |url=http://www.heise.de/mobil/meldung/Gefaelschte-SD-Karten-151283.html |access-date=2013-06-07 |archive-date=2013-06-23 |archive-url=https://web.archive.org/web/20130623055703/http://www.heise.de/mobil/meldung/Gefaelschte-SD-Karten-151283.html |url-status=dead }}</ref><ref name="c't2013-häufiges">{{cite web |url=http://www.heise.de/mobil/meldung/Smartphones-waehlerisch-bei-microSDHC-Karten-1825259.html |title=Smartphones wählerisch bei microSDHC-Karten |publisher=Heise mobile – c't magazin für computertechnik |date=2013-03-18 |access-date=2013-06-09 |last=Feddern |first=Boi |language=de |archive-date=2019-01-01 |archive-url=https://web.archive.org/web/20190101010525/https://www.heise.de/mobil/meldung/Smartphones-waehlerisch-bei-microSDHC-Karten-1825259.html |url-status=live }}</ref> Software tools exist to check and detect [[USB flash drive#Counterfeit products|counterfeit products]],<ref name="h2testw">{{cite web |title=H2testw heise Download |language=de |url=https://www.heise.de/download/product/h2testw-50539 |access-date=2016-11-26 |archive-date=2016-11-26 |archive-url=https://web.archive.org/web/20161126111115/https://www.heise.de/download/product/h2testw-50539 |url-status=live}}</ref><ref name="f3">{{cite web |title=F3 by Digirati |url=https://oss.digirati.com.br/f3/ |access-date=2016-11-26 |archive-date=2016-11-24 |archive-url=https://web.archive.org/web/20161124080508/http://oss.digirati.com.br/f3/ |url-status=live}}</ref><ref>{{cite web |url=https://www.usbdev.ru/articles/detect_controller/ |language=ru |title=Определение модели контроллера и памяти флешки |date=20 February 2013 |trans-title=Detecting controller model and memory type of flash drive |publisher=usbdev.ru |access-date=2018-01-06 |archive-date=2023-06-24 |archive-url=https://web.archive.org/web/20230624000054/https://www.usbdev.ru/articles/detect_controller/ |url-status=live }}</ref> and in some cases it is possible to repair these devices to remove the false capacity information and use its real storage limit.<ref>[http://fixfakeflash.wordpress.com/2008/12/11/about-vid-pid-repairing-counterfeit-flash-drives-steps-to-succeed/ "About VID PID Repairing Counterfeit Flash Drives – Steps To Succeed"] {{Webarchive|url=https://web.archive.org/web/20110109230403/http://fixfakeflash.wordpress.com/2008/12/11/about-vid-pid-repairing-counterfeit-flash-drives-steps-to-succeed/ |date=2011-01-09 }}, fixfakeflash.wordpress.com, retrieved November 16, 2010</ref>

Detection of counterfeit cards usually involves copying files with [[random data]] to the SD card until the card's capacity is reached, and copying them back. The files that were copied back can be tested either by comparing checksums (e.g. [[Md5sum|MD5]]), or trying to [[Data compression|compress]] them. The latter approach leverages the fact that counterfeited cards let the user read back files, which then consist of easily compressible uniform data (for example, repeating [[0xFF]]s).