Jerome Taylor: Gone but not forgotten: how deleted emails can be traced

Think your email has been wiped when you press the delete button? Well think again. Removing information from a hard drive or server may seem like a simple one-click procedure, but permanently deleting data is all but impossible without military grade software.

We've all read about how police investigators can rebuild a shattered hard drive to convict paedophiles. With the correct software, forensic investigators can sift through broken data and rebuild it, a little like piecing together a jigsaw puzzle.

Even if you mistakenly delete photos from your camera's memory card, you can often get 60 per cent of the pictures back by running the card through over-the- counter recovery software.

Emails are no different. When you send someone a message it will travel through – and be stored on – a whole host of servers, from a sender's hard drive, to a company's server, through various email gateways and then on to the recipient's server and hard drive.

The only way to delete such an email permanently would be to wipe it at each and every one of those steps. If investigators have access to those steps they can start to piece together the gaps.

If large tranches of News International emails have been deleted it will make it harder for police to piece together what was being sent and by whom.

But they should still be able to get access nonetheless.

To wipe a hard drive it is possible to buy military grade deletion software which effectively wipes the slate clean of any trace of the original file. But emails – which bounce from server to server – are much harder to disappear.