Ajit Gaddam on Security & Technology

The Great Zero Challenge: A challenge to confirm whether or not a professional data recovery firm or any individual(s) or organization(s) can recover data from a hard drive that has been overwritten with zeros once. All they used is the Unix dd command using /dev/zero as input to overwrite the drive.

They are doing this because many people believe that in order to permanently delete data from a modern hard drive that multiple overwrites with random data, mechanical grinding, degaussing and incinerating must be used and even physically destroy them just to be extra safe.

As far as challenges go, this is one that many will pass, because no data recovery firm claims to be able to do zero recovery other than those with access to electron microscopy tools.

Many professional recovery firms for most part use tools that scan through the partition and file table area and perhaps even the entire disk to locate data that has either been marked erased or had references removed (for a full disk scan) and then restoring it. Perhaps they’ll also move the spindle from a dead drive into a new case to complete the operation, but I doubt there are many companies that will actually do electron force microscopy for you and even fewer that will do it at anything other than an astronomical fee.

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Besides manual security hardening of a Linux OS, let’s check out a free open-source tool to automate and simplify the process. Bastille will disable unnecessary services and install operating system updates as well as configure a firewall, enforce password policies, create a second root-level account and more. What’s nice is that Bastille leads the user through a simple series of yes/no questions, giving a detailed explanation of why each question is asked and what will happen if ‘yes’ is chosen. It doesn’t merely expect guesswork, nor does it blindly alter your system – instead, it genuinely hardens your computer and educates on security in the process.

The good thing is that you’re also not locked in to Bastille’s changes should you decide some of the setting changes weren’t for you. Running RevertBastille automatically restores the state of all config files and settings to just how they were before Bastille made any changes. Obviously, if you make changes to your system manually after running Bastille, you will lose these too so it is best to test changes as soon as possible after applying to ensure you won’t harm anything else if you need to revert.

Unfortunately, Bastille is not for everyone: versions exist for Red Hat, SUSE, Debian, Gentoo and Mandrake (as well as non-Linux UNIX variants HP-UX and MacOS X). If you do run one of those systems, you really are well-advised to run Bastille. You can download the latest version from SourceForge.

Let’s give Bastille a run-through.
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Sometimes when running through a CSV or any kind of a log file, you may encounter lists with a lot of duplicates. I will show an example of the simplest order here.

Say, you have a duplicates.txt that goes

one
two
three
one
four
two
four

Now, how to remove duplicates from a list such as the one shown above. If you use a command such as

sort - u < duplicates.txt or cat duplicates.txt | sort | uniq

you may end up with a list that while stripping out the duplicates, does not keep the original order

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A lot of us who use Linux at work/school or have always grown up using Unix commands and using the Unix shell for years and more often than not, there are instances where a ls command comes more naturally than the dir command at the command prompt when using Windows.

For the most part, a lot of us work around this drawback using the excellent tool: Cygwin. Cygwin is available for windows users here.The Cygwin tools are ports of the popular GNU development tools for Microsoft Windows. They run thanks to the Cygwin library which provides the UNIX system calls and environment these programs expect.

With these tools installed, it is possible to write Win32 console or GUI applications that make use of the standard Microsoft Win32 API and/or the Cygwin API. As a result, it is possible to easily port many significant Unix programs without the need for extensive changes to the source code. This includes configuring and building most of the available GNU software . Even if the development tools are of little to no use to you, you may have interest in the many standard Unix utilities provided with the package. They can be used both from the bash shell (provided) or from the standard Windows command shell.

While Cygwin would be an obvious choice for many Unix/Linux power users, there is an excellent and a much simpler alternative to using Cygwin. In this article, I will show you how to run your Unix commands right in the windows command prompt.

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