Gadget speak

Our security expert explains how to permanently delete those secret dossiers.

Deleting files permanently

"Manuscripts do not burn" proclaimed the devil in Mikhail Bulgakov's epic tale 'Master & Margarita'. Well, digital storage devices definitely do, if that's the solution you favour for retiring old media. There are other ways, however, to effectively delete unwanted data, sanitise hard drives and flash media storage devices.

As previously mentioned in the Trade Secrets column (March 17, 2009) - deleted or corrupted images on digital cameras can be restored. Computers and digital media devices cannot erase data. The delete command only modifies the relevant file descriptors in the operating system and previously assigned disk space is marked available for overwrite. The icon disappears from screen but the content is still there. Formatting has a more or less similar effect. This holds true for most personal computers, PDAs, digital cameras and flash memory.

Aside from degaussing, burning, microwaving or ingesting your digital storage device, there is only one sure method of deleting unwanted data whilst preserving use of the device itself. Every addressable block occupied by the original files needs to be overwritten with ASCII NUL bytes (zeroes). Experts recommend using several different patterns (or passes). For example, the US Department of Defence enforces three to seven passes, depending on the document's sensitivity, when requiring its permanent and secure deletion (also referred to as wiping).

Today's software options have made this process incredibly easy. Eraser for Windows and Permanent Eraser for the Mac OS X are free tools that can wipe files and entire disk drives using the specified number of passes. Eraser can also wipe all remnants of past files stored in the empty space of your hard drive or media device. This feature is known as a free space wipe. On the Mac OS 10.4 and higher it can be achieved from the Disk Utility function by selecting Erase and then the Free Space button.

Don't forget to delete the temporary files on your computer, collected whilst browsing the Internet, working with documents and media. Ccleaner for Windows and Onyx for MAC OS/X can locate and delete them for good.

Once all necessary software is installed, run a free space wipe, followed by a clean up of your temporary files. From now on, use wiping tools to delete unnecessary data and don't think twice about sharing your PC again! [new window] [new window] [new window] [new window]

Technology clinic

Boosting Signals

I read with interest 'Spaghetti Me Not' (E&T Vol 4 #3) as my business is primarily concerned with home installation of high-end audio equipment. A customer wants to drive a PC with a keyboard, monitor and mouse situated in a different part of the property. I'm thinking wireless USB. Is this possible?

David Taussig, London

Wireless USB, as its name suggests, has been designed as a wired USB replacement. It depends how far the peripherals are from the PC. If it's more than 10m, you are going to encounter problems. Perhaps there is a way of repeating or boosting the signal, but our friends at CEDIA and the Wireless USB Forum cannot think of anyone manufacturing such a device. Perhaps our readership may provide a better answer than I can.

More Freesat advice

The advice given - to get Freesat - is good and solid. We have without problem used FreeSat from Sky all over France, Germany, Belgium, and Holland while caravanning and I know others who use it in Spain also.

However, the comment about not being able to get a receiver was erroneous. If you toddle along to your nearest DIY shed - Leroy Merlin or Bricoman are the best starters - you should be able to get a complete satellite kit for well under €100. This comprises a 80cm dish, a reasonably good LNB (the signal-catching bit that fits on the end of the arm of the dish) and a digital receiver.

Do make sure however that the receiver is the 5000 or 5500 channel variety as those with fewer channels often do not have Astra 28.2E programmed - it should say on the box. I have a Vtronic bought from L-M for about €60 and it works a treat. It's true, you will not be able to get a 'Freesat' box per se, but all you will miss with a locally sourced box is the Electronic Programme Guide.

If you want a Freesat box then look at The only other bits you will need are a wall mount (a square plate with a right-angled tube protruding from it) plus fixings, and a length of suitable satellite cable - that is the variety with a braid and a copper foil sheath. The necessary F-type plugs are supplied with the dish kit. If you don't have one you will also need a compass to direct the dish - somewhere around 145° - and a satellite finder is also useful, at around €5 or less if you get it on offer at Lidl.

Don't be afraid, have a go. I've been using satellite when in the caravan for three years without problem, save one occasion of torrential rain at Verdun-sur-le-Doubs and it cut the signal to near nothing (but I use only a 60cm dish - 80cm will get a better signal).

There is something slightly arcane about sitting on a beautiful campsite at Obernai in Alsace sipping a glass of the local Sylvaner whilst watching Paul the weatherman on 'Look North' from Leeds!

 Andrew Woodthorpe FIET, Harrogate, UK

Thanks are due to the several letters in response to this question which we have passed on and will publish on our website, [new window].

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