How to create your own free computer forensics kit on a USB drive

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The super-sleuth detectives in TV show CSI have some very nifty tools to help solve crimes. But the need to keep things interesting and wrap the show up in an hour means the technology used in each episode bears little resemblance to the work of real forensic experts. Or does it?

When it comes to computer forensics, today's tools are becoming more advanced, leaving fewer places to hide information. This tension between fact and fiction took on a whole new dimension when Microsoft's police-only forensic toolkit was leaked on the internet. Reports say that it has more in common with CSI than The Bill.

We're going to show you how to mimic Microsoft's offering using open-source software to unlock Windows accounts, investigate suspicious activity, see any file on a Windows disk and even peruse files that others believe have been permanently deleted.

Forensic toolkit

During November 2009, it was announced that someone had leaked Microsoft's secret crime-fighting software online.

Described as a collection of programs linked by a sophisticated script, hackers and other cybercriminals had been dying to get their hands on it for some time. Now it's reportedly available to anyone brave enough to download and install it.

The Computer Online Forensic Evidence Extractor (or COFEE for short) has been available to police forces since at least summer 2007, and is designed to gather forensic evidence at crime scenes and during raids from the still-running PCs of suspects and victims.

COFEE reportedly takes the average police officer about 10 minutes to master, and comes supplied on a bootable USB pen drive. It enables trained officers to gather evidence from a running system without the need to call in cybercrime specialists, thereby speeding up investigations.

The USB drive itself is said to contain a package of about 150 forensic programs that enable an investigator to record sensitive information like internet history files and complete practical tasks like deleting Windows passwords. It also enables them to upload the recorded data for further analysis.

By April 2008, it was reportedly in use by over 2,000 law enforcement officers throughout 15 countries. At the time of the leak, Microsoft claimed that COFEE was nothing more than a collection of commercially available programs brought together in a single handy package, which it makes available free of charge (if hitherto secretly) to help combat computer crime.

If that's true, then is it also possible to create your own version of COFEE using free, open source software that will grant you complete access to a Windows computer?

The answer is a resounding yes, but we must stress that using what you're about to learn for malicious purposes on a computer you don't own isn't big and it's certainly not clever. Don't use the following information to try to hack other people's computers or networks. Without the in-depth knowledge required to cover your tracks, you'll be caught and will probably face prosecution.

If you hack computer systems in the US and get caught, you should be prepared to undergo a one-sided extradition process and go through a judicial system that will put you on a par with hardened terrorists before forcing you to serve a long prison sentence.

There are plenty of commercial computer forensics systems around these days, but many of them cost serious money or are only available to the police. However, the open source community has a solution in the form of a special Linux distribution called Backtrack 4.

Introducing Backtrack 4

Backtrack 4 is based on a stripped-down version of Ubuntu Linux, which is a popular choice for home users because of its ease of installation and use. The makers of Backtrack 4 have stacked the application with special security and forensics tools. These make it extremely useful to network security specialists and police forces, as well as anyone interested in knowing exactly what's happening on their own networks and any second-hand machines they've bought.

Despite being Linux-based, Backtrack will grant you complete access to data stored on computers running any version of Microsoft Windows. That's because Windows isn't running when Backtrack is booted from a DVD or USB pen drive.

Linux can read Windows disks, but it doesn't obey the file permissions, so the machine's hard disk simply seems to contain a lot of files waiting to be accessed. As well as booting and running directly from a DVD as a Live CD installation that never installs on your computer, you can also install Backtrack on a hard disk as the only operating system, or next to an existing Windows installation.

If you plan to install Backtrack on a USB pen, you'll need one with a minimum 2GB capacity. This booting option brings Backtrack closer to Microsoft's COFEE than any other option.

First, you need to download the Backtrack 4 ISO file, which is just under 1.6GB. You can download it from the Backtrack site directly or click the 'Torrent' link on the same page. There are multiple sources from which you can leech parts of the file in parallel, so in practice it's faster to download the ISO as a torrent.

Once the ISO has downloaded, use it to make a bootable DVD. We've listed a free and easy to use CD/DVD package capable of making bootable disks in the Resources section. When that's done, test your work by ensuring your BIOS is set to boot from CD/DVD before attempting to boot from your hard disk, then insert the DVD and reboot the PC. Select the option to boot with a screen resolution of 1,024 x 768.

When Backtrack has booted, you'll see a command line. To start a desktop environment, enter the command startx and press [Enter]. After a few seconds, the standard KDE desktop will start.

Find your way around

Backtrack is loaded with all the obscure little utilities used by professional security consultants. Many of them are fiddly command-line programs, but a lot have graphical front ends that make them simple to use.

Hover your mouse over the icons on the menu bar at the bottom of the desktop and KDE will tell you the name of each one. We'll use the names that appear when you do this to make thing easy to identify here.

The network interface cards are designed for network security work, and are disabled by default when you boot up Backtrack. This is because if anyone (or anything) is listening to network traffic, the last thing you want to do is announce your presence by requesting an IP address over DHCP.

To enable networking, click the black Konsole icon to open a terminal window, then enter the following command:

/etc/init.d/networking start

After a moment or two, during which lots of verbiage scrolls up the screen, open Firefox (the icon is next to the terminal on the menu bar) and enter Google as a URL. You should see the world's favourite search engine appear.

Much like the Start button in Windows, the left-hand icon on the menu bar brings up the installed programs and system configuration options. This is called the K menu and is organised into subject areas. The one we're most interested in is the first: 'Backtrack'.

Click on this and you'll see a submenu containing categories of hacking programs, with which Backtrack has been preloaded. Clicking one of these reveals nested subcategories right down to individual programs.

Map the neighbourhood

Let's begin by scanning the local network for hosts (another name for networked computers). Starting from the K menu, select 'Backtrack | Network Mapping | Identify Live Hosts | Autoscan'. A wizard will appear. Click 'Forward' and you'll be asked for the name of a network to scan.

Leave this as 'Local network' and click 'Forward' again. The next screen asks where the network is located. We're scanning the local network, so accept the default of it being connected to your computer by clicking 'Forward' once more.

Next, select the default network adaptor. This will usually be called 'eth0'. If you don't see any adaptors in the pull down menu, it's because you didn't start networking earlier. Close Autoscan, start networking and run Autoscan again. Click 'Forward' one last time to confirm what you've asked Autoscan to do, then maximise the user interface that appears so you can see everything.

Autoscan now contacts every possible IP address on the local subnet to see if there's a machine connected to it. If there is, it adds an entry to the left-hand pane. Notice that in some cases, Autoscan can even tell you the username that's logged in.

When you select a host, Autoscan will attempt to gain more information about it for you. A wizard will also appear, asking you to add it to the Autoscan online database. Cancel this. You can go between tabs between the interface's right-hand panes to display a summary of the machine, detailed information or an inventory.

Autoscan works by sending a stream of specially crafted packets to each host in turn. These are designed to return information about the running system and can give away a surprising amount of information. Autoscan is a useful tool for detecting whether your neighbours are leeching your Wi-Fi, for example. If you don't recognise a host, it's probably an intruder – so up your security!

Wipe passwords

Logging into a Windows system is easy using Backtrack, even if you don't know any of the usernames or passwords that have been set up. That's because you can use a utility bundled with Backtrack to remove the password on any Windows account, including administrator accounts.

This is possible because of a file called the SAM (Security Access Manager), which is normally locked by the Windows kernel so that no one else can read it. This is modifiable while Windows isn't running.

First, we need to find out where the system's hard disk resides in Linux. To do this, click the Konqueror icon on the desktop menu bar. This will open the Konqueror desktop browser. Click the 'Storage media' link. If you don't see anything right away, press [F5] to refresh the view.

Among the media that Backtrack knows about on your system, you'll see your hard disk. Click this and you'll see the folders in C:\, which is useful if you need to copy, add or modify files without logging into Windows directly.

Now select the Home icon on the Konqueror toolbar (the one that's shaped like a house) and click the blue 'up' arrow next to it. Click the Media folder, and then the 'Hard disk' icon again. The location bar will change to give the name we must use to access the disk. It'll be something like '/media/disk'

Now, from the Start menu, select 'Backtrack | Privilege Escalation | Password Attacks | Chntpw'. 'Chntpw' stands for 'Change NT Passwords' and it works on all versions of Windows. When you run the command, a terminal window opens. You can ignore the verbiage on the screen and enter the following command:

chntpw -i /media/disk/Windows/System32/config/SAM

The capitalisations are very important here – 'chntpw' is all lowercase. If your Windows partition is called something other than 'disk', put its name in place of this in the command.

Press [Enter] and a text-based menu will appear. Select 'Option one' and press [Enter] again. This gives you a list of the Windows user accounts. Type the name of the account you want to change (taking care to use the correct case for each letter) and then press [Enter].

Chntpw displays lots of details about the account and gives you a number of options. Select 'Option one' and the password will be removed from the account. To exit, type ! and press [Enter], then press [Q] and hit [Enter] again. Chntpw will ask if you want to write the hive files. You do, so press [Y] followed by [Enter].

If you now reboot into Windows, you'll be able to log into the account you've changed without being prompted to enter a password.

Recovering deleted files

Many people believe that when they delete a file and then empty the Recycle Bin, it's gone for good – but this isn't the case. Windows, like all modern domestic OSes, simply marks the sectors on the disk occupied by the deleted file as available for future reuse. It would be inefficient to overwrite the data those sectors contain until new data is ready to be stored.

In the meantime, the old file is still there, available to be read by anyone with access to a file recovery utility. Backtrack contains several such applications. Among the easier to use is PhotoRec, which is capable of scanning a hard disk and recovering a comprehensive list of all files marked as deleted.

In fact, it can recover far more than just files deleted by users, including temporary files left over from when the operating system was installed. This means it's a good idea to have a spare USB pen drive handy to store the recovered files for later perusal, because they can easily run into the thousands.

To get going, insert the drive and run Konqueror. Click 'Storage media' and then select your USB pen drive to ensure that Backtrack is aware of it. You can leave Konqueror open and check the scan's progress later.

Now run PhotoRec by navigating to 'Backtrack | Digital Forensics | Forensic Analysis' and then selecting 'PhotoRec'. The program itself runs on the command line, but it's menu driven, making it easier to use.

When PhotoRec runs, it first presents you with a list of the hard disk partitions on the computer. In the case of a Windows-only machine, there'll probably be only one large one. However, in some Windows 7 installations, there may be a second, small partition that the system uses to store recovery data.

Use the up and down arrow keys to select the main partition, then press [Enter] to continue. PhotoRec can understand a large number of partition table types and will automatically identify the one used on your disk, so accept the default on the next screen by pressing [Enter] again.

The next screen enables you to specify the file types to recover. Use the left and right arrow keys to highlight 'File Opt' at the bottom of the screen. Next, press [Enter]. The resultant display will give you a long list of all the recognised types.

If you only want to recover one file type (JPG, for example), press to deselect everything, then scroll down to the relevant type and press [space]. You can use the [Page up] and [Page down] keys to navigate through the list more quickly.

Once you're happy with your file type selections, press [Enter] and select the filesystem you want to scan. Use the left and right arrow keys to select the 'Search' option, then press [Enter]. This presents you with a choice of file system types.

For a Windows filesystem, make sure you select 'Other', then press [Enter]. On the next screen, select 'Free' to ensure that the program only scans disk sectors that are marked as free space. Press [Enter] again to continue. You'll now be asked where to store the recovered files.

The default is the directory '/usr/local/ bin', which is on the boot media. Press the left arrow key three times to get back to the root directory, then press the down arrow key repeatedly to navigate to the media directory. When you reach it, press [Enter] to see the media connected to the system.

One of the devices you find should be the USB pen drive you inserted and navigated to in Konqueror just a moment ago. Select this and press [Enter] again. Finally, press [Y] to begin recovering deleted files. The extraction process can take quite a while, depending on how much free space there is to scan on the disk and the number of file types you've specified.

As the scan progresses, the number of files of each type will increase. PhotoRec creates a long list of subfolders in which it stores all the files it's recovered. By perusing these, you may be able to locate some interesting or even incriminating pictures and other documents.

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