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My system is encrypted using Full Disk Encryption, i.e. everything except /boot is encrypted using dmcrypt/luks. I am concerned about Cold Boot Attacks.

Prior work:

Can you please provide instructions on how to wipe the RAM once Ubuntu is shutdown/restarted?

Thanks for your efforts!

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2 Answers 2

You could use sdmem.

sudo apt-get install secure-delete

To make it run at every shutdown, we'll create an Upstart job file called memory_wipe.conf.

Note: this is one command. Copy/paste it in its entirety!

echo '# upstart config - wipes memory on shutdown

description  "Wipes memory on shutdown"

start on (runlevel [016] and stopped gdm)

script
    sdmem
end script' > sudo tee /etc/init/memory_wipe.conf

Restart your computer and upon the next reboot, your RAM will be wiped securely!

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Isn't kexec into a new kernel required? Otherwise the old kernel does not get overwritten? –  James Mitch Aug 21 '12 at 9:02
    
Wiping the RAM when gdm stops might be a bad idea, since it causes an unclean shutdown? sdmem might overwrite itself or the kernel, therefore crashing the system without wiping the complete the RAM? –  James Mitch Aug 21 '12 at 9:03
    
Why are the implementations in the Live CD's (prior work) so complex and these so simple? Too simple to be safe? –  James Mitch Aug 21 '12 at 9:07

Take a look at this thread

http://ubuntuforums.org/showthread.php?t=1500936

If you still want to do it then:

Look for secure-delete in Synaptic

The Secure-Delete package comes with four commands:

srm - Secure remove; used for deleting files or directories currently on your hard disk;

smem - Secure memory wiper; used to wipe traces of data from your computer's memory (RAM);

sfill - Secure free space wiper; used to wipe all traces of data from the free space on your disk;

sswap - Secure swap wiper; used to wipe all traces of data from your swap partition.

Source: http://ubuntuforums.org/showthread.php?t=1008111

And to make it run when you want:

To execute a script upon rebooting Ubuntu

Put your script in /etc/rc0.d Make it executable (sudo chmod +x myscript) Note: The scripts in this directory are executed in alphabetical order

The name of your script must begin with K99 to run at the right time. To execute a script at shutdown

Put your script in /etc/rc6.d Make it executable (sudo chmod +x myscript) Note: The scripts in this directory are executed in alphabetical order

The name of your script must begin with K99 to run at the right time.

Source: http://en.kioskea.net/faq/3348-ubuntu-executing-a-script-at-startup-and-shutdown

If you do not know how to make a script:

Make a text file in an easy to find directory:

Code:

#!/bin/bash

COMMAND1

COMMAND2

COMMAND3`

Use the shebang line that I have given. Replace COMMAND1 and etc with the command you would like the script to run.

Save the text file and then you have to make it executable. For this I will assume that the the file is called "test.sh". To make it executable:

chmod 775 test.sh

Then you can run the script:

./test.sh

Source: http://ubuntuforums.org/showthread.php?t=928839

Hope this helps,

Leinardo

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Why use the deprecated rc runlevel system? –  James Mitch Aug 21 '12 at 9:04
    
I don't think this can work. Unless kexec into a fresh kernel with smem, the old kernel may overwrite itself or smem and not everything is cleaned. –  James Mitch Aug 21 '12 at 9:06

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