According to iOS researcher Jonathan Zdziarski, WhatsApp doesn’t actually delete chats that you have deleted – until a much later date. In essence, the software retains and stores a forensic trace of the chat logs even after the chats have been deleted, which would really delight anyone with interest in your chat history. And if you have it backed up remotely, this same data are also purportedly recoverable.
WhatsApp is based on SQLite which is used not only by them but also by iMessage and a few others, which without mitigation, would be exposed to this issue.
What happens here is the SQLite does not exactly clears and deletes databases after you delete it – it just mark’s these data as free and available for data to overwrite it. But these free data are not overwritten until the database is out of clear free memory before it ‘recycles’ this space. Hence, depending on your available space, it may take weeks, months or even years before they get overwritten.
But what’s the catch? If you don’t do remote backup’s especially to iCloud, then your pretty much safe, as long as you keep your phone to your hands only.
