If you watch any crime dramas on television you have seen the technicians do some magic and recover data off an disc that was erased. I was curious how secure Secure Digital cards and flash drives were. The short answer is that the last data on the cards can be recovered even after formatting or erasing the cards.
I recently donated some cards and flash drives to a local charity. When travelling I often take pictures of receipts and use them to balance my checkbook when I return. If these documents were on my desk I would shred them once the checkbook was balanced. Using the same logic I wanted to make sure these cards were empty before donating them.
There is no way that I have found to erase a card or flash drive without destroying them. However since they only hold the last data placed on them you can overwrite them with something you dont mind sharing. Here are the steps I took before donating these items.
1: I put as much music on the card as I could.. Any files will work just make sure you wouldnt mind sharing the data. If you would post it on facebook its a good candidate for this. (I have friends who use huge jpeg images of landscapes for this)
2: I placed the card in a camera, pointed it at the wall and shot video until my camera said the card was full. This filled the last little bit of memory on the card.
3: I reformatted the cards.
At this point I have an “empty” card and the residual memory is full of safe data.
Some points to remember here.
Some images and data could be recovered after a card is erased or deleted. It is less likely that data could be recovered after formatting a card but possible. Either of these would take special software, but it is available.
The controller on the SD cards spreads the information around on when writing on a card. This insures that you dont wear out one spot on the cards. It also means that you have to completely overwrite the card before donating it.
Hopefully this article answered your question if you want to learn more about SD cards I have a website at.