Those rumours were true - computers [https://learn.equalit.ie/wiki/Destroying_data cannot delete data]. Information previously deleted on your computer, USB or SD card by using the standard delete > empty bin method, can be recovered. In order to destroy data you need to overwrite its physical location on the disk with new information. Specific tools exist for this purpose including [https://ssd.eff.org/en/module/how-delete-your-data-securely-windows Bleachbit for Windows] and [https://ssd.eff.org/en/module/how-delete-your-data-securely-linux Linux], as well as [https://securityinabox.org/en/guide/ccleaner/windows CCleaner] and [http://sourceforge.net/projects/eraser/ Eraser] for Windows. MacOS users can follow the techniques mentioned in [https://ssd.eff.org/en/module/how-delete-your-data-securely-mac-os-x this guide] or recommendations regarding SecureTrash on the [https://support.apple.com/kb/PH18638?locale=en_US&viewlocale=en_US Apple website].