Police probe Downing Street hard drives

Police are using data mining techniques to examine hard drives taken from the Prime Minister's office

Police are using forensic analysis to examine hard drives taken from the Prime Minister's office using data mining techniques designed to find deleted information, according to press reports.

"Quite clearly, in the past few days, the police have found something significant, possibly a file dump of some kind," a source told The Daily Telegraph. "They have been using specific software of the type they use in complex fraud cases."

The analysis was carried out before the dawn arrest of the Prime Minster's aide, Ruth Turner, on charges relating to offences under the Honours (Prevention of Abuses) Act 1925.

The newspaper suggested that the police were frustrated with their progress after twice asking for all documents relating to the case and only receiving a small amount of information.

The investigation has been ongoing for over a year and more arrests are expected soon.

Forensic analysis is commonly used to detect deleted information. Once data is deleted the actual information remains in place on the hard drive and only the header identifying it on the hard drive controller is wiped out.

The information may be slightly scrambled by a reformatting of the hard drive but the only way to fully delete files is to record data over the drive repeatedly so that the original information is totally wiped.