Feeds

Clearing swap and hibernation files properly

Two neglected open books

  • alert
  • submit to reddit

Top 5 reasons to deploy VMware with Tegile

Privacy workshop Most privacy-conscious users are familiar with deleting files securely, that is, destructively with overwriting and with wiping free space on their disks. But two items that often get overlooked are the swap file (or swap partition), and the hibernation file.

Let's start with the swap file. This is an area of your hard disk where data previously held in RAM is written, and later read, to "free up" physical memory and make it available for other tasks. Data swapped from RAM to disk is sometimes called "virtual memory". Your computer can read from RAM much faster than it can read from the disk, but RAM is expensive, whereas disk space is comparatively cheap and usually plentiful. Thus, it's not unusual for a system to have a swap file of 1GB or more.

Unfortunately, your swap file knows a lot about you. Pretty much anything you do with your computer can leave traces there. Files you've opened and their contents, websites you've visited, online chats you've had, emails you've sent and received, virtually anything can end up archived in it for quite a long time - months, and even years. You can delete, even wipe securely, the original data, and still your swap file might tell on you by retaining duplicate traces of your computing behaviour. Forensics practitioners consider the swap file to be a real bonanza of data traces, because swapping is an automatic, background process that users - even privacy-conscious ones - can't control completely.

So, what data gets swapped to disk? No one can say: it depends on conditions and memory needs peculiar to each system. Not all data is swapped to disk, but virtually any data might be swapped - even passwords, potentially.

In fact, it's possible that the plain text versions of encrypted files could turn up in the swap file: perhaps the content was swapped to disk before encrypting or after decrypting - that is, when a user is viewing or editing the plain-text content of these files. A good encryption utility will have its own viewer and editor designed to prevent swapping the plain-text data. But are you certain that it works as it should? And what happens if you copy and paste between two decrypted files, or between two files that you intend to encrypt later? Clipboard contents can certainly be swapped.

So, what are the solutions? First, and most obviously, don't use a swap file or swap device. If you've got plenty of RAM, you might not need anything more. Some Windows applications, games, etc, require a swap file even when there is an abundance of RAM, so not everyone can use this option. But Linux users can almost always get away with not using a swap partition if they have plenty of RAM, say 1GB or more.

The next approach is to perform a manual, secure wipe of the swap file on a regular schedule with the help of an inexpensive utility like BCWipe for Windows users, or a free utility like LinuxWipeTools for Tuxers.

Security for virtualized datacentres

More from The Register

next story
'Kim Kardashian snaps naked selfies with a BLACKBERRY'. *Twitterati gasps*
More alleged private, nude celeb pics appear online
Home Depot ignored staff warnings of security fail laundry list
'Just use cash', former security staffer warns friends
Hackers pop Brazil newspaper to root home routers
Step One: try default passwords. Step Two: Repeat Step One until success
UK.gov lobs another fistful of change at SME infosec nightmares
Senior Lib Dem in 'trying to be relevant' shocker. It's only taxpayers' money, after all
Who.is does the Harlem Shake
Blame it on LOLing XSS terroristas
Snowden, Dotcom, throw bombs into NZ election campaign
Claim of tapped undersea cable refuted by Kiwi PM as Kim claims extradition plot
Freenode IRC users told to change passwords after securo-breach
Miscreants probably got in, you guys know the drill by now
THREE QUARTERS of Android mobes open to web page spy bug
Metasploit module gobbles KitKat SOP slop
BitTorrent's peer-to-peer chat app Bleep goes live as public alpha
A good day for privacy as invisble.im also reveals its approach to untraceable chats
prev story

Whitepapers

Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
WIN a very cool portable ZX Spectrum
Win a one-off portable Spectrum built by legendary hardware hacker Ben Heck
The next step in data security
With recent increased privacy concerns and computers becoming more powerful, the chance of hackers being able to crack smaller-sized RSA keys increases.