Once deleted, can text messages be retrieved?

Clearing or deleting your messages on your devices doesn't mean the data is permanently gone, it's just been filed away differently.

Yes they can, so if you’ve been having an affair or doing something dodgy at work, beware! Messages are laid out on the SIM card as data files. When you move messages around or delete them, the data actually stays put. All you’re doing is telling the phone to point at the files in different ways. Deleting a message from the inbox, for instance, just tells the phone not to point to it any more when it’s listing the contents of that folder.

Even when you ‘permanently’ clear messages, you’re simply getting the phone to stop listing it in the deleted items folder. You can’t recover such texts on the phone itself, but there are plenty of commercially available software packages you can buy that allow your PC to read data directly from a SIM card. Some of the more advanced tools figure out the file structure on the card, thus allowing those long-hidden deleted messages to be resurrected.

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