Popular online messaging service WhatsApp has made all sorts of security news in recent years. WhatsApp now provides end-to-end encryption in a privacy-centred way, where WhatsApp itself never holds the cryptographic secrets that it would need to snoop on your messages as they pass through its service. iOS app stores its messages in a database that uses the popular and widespread SQLite toolkit. When you delete messages from the WhatsApp database, SQLite marks the records so they can be re-used later, but until the database fills back up again (which could take a long time if you delete lots of messages at once), the raw bits-and-bytes of the old data will remain behind.”]