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Clearing swap and hibernation files properly

Two neglected open books

Sensitive data asleep

Now for hibernation, or suspend-to-disk, on Windows 2K and XP. Enabled by default on XP, this gimmick takes a snapshot of memory and writes it to disk so your computer can hibernate and "wake up" more quickly than it could from a dead stop. In practice, it's not that much help, and few users express much enthusiasm for it. So its benefits are questionable, while it poses a serious challenge to good data hygiene. The size of the corresponding hidden file, called hiberfil.sys, will roughly match the amount of RAM on the system.

Naturally, an incredible amount of sensitive data could be dumped to disk when hibernation is activated. So if you're at all concerned about privacy and data hygiene, this file has to go, and the area it occupies has to be wiped properly.

1. Begin by disabling hibernation. Go to Control Panel ==> Power Options, to launch the Power Options Properties dialogue box. Select the tab labelled "Hibernate", and clear the tick-box beside the option, "Enable hibernation". Click the Apply button, close the dialogue box, and reboot your machine.

2. Next, open Windows Explorer and navigate to the root directory, i.e., My Computer ==> Local Disk (C:). Look for hiberfil.sys, and delete it if it's present. Now, empty your Recycle Bin.

3. Finally, perform a secure wipe of your disk's free space and file slack space.

As far as I know, current Linux distros do not hibernate or suspend-to-disk by default, although a user can implement it using the swap partition as the hibernate file. In that case you would need a swap partition about twice the size of system RAM, and you will have to recompile your kernel, as certain features need to be built in to the kernel, rather than being loaded as modules. But clearing hibernation data properly is as easy as running the script as described previously.

So once again, when it comes to privacy and security, Linux users have it a lot easier than Windows users. And cheaper, too. ®

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