SANS Digital Forensics and Incident Response Blog: Author - Keven Murphy

Custodians of Digital Evidence

Let's think like a system administrator for a moment....

Here is the scenario:

You're the corporate incident handler/digital forensics person and you've just finished your latest case. The finished forensics report has been handed off to your boss, human resources, and the legal team. You are looking at your raid 5 volume with all of the data the case generated. With 500 gigabyte drives and terabyte drives almost a standard now, the case data might be nearly that big. So you back up your data and tools you used on the case to your DLT tape drive or another hard drive, wipe your drives, and pack the media away for storage.

Now it is four and half years later, legal counsel calls you into their office to tell you that the ex-employee has decided the sue. Not a problem, you've got your all of the case data backed up. It is just a matter of restoring it and providing copies to counsel as required.

But here is the problem, the DLT drive you have been using,

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Making Reviewing Files From Data Carving Easier: Documents

This is my second installment on dealing with files recovered through the use of data carving tools. As I said in my previous post on data carving, that having to do corporate forensics, I end up having mountains of files to go through after running data carvers like Foremost/Scalpel or Photorec. Most of the programs out there either can't handle the amount of files or are very time consuming to work with. One of the worst ones to go through was document files. You know the

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Making Reviewing Files From Data Carving Easier: Images

Background

I usually do a lot of data carving. With 500 gig drives becoming the norm in machines, the recovered files I see from data carving is huge. Nothing like having to review 10000+ jpegs and having to review each one. I had a lot of issues trying to find something to review that many images. After trying many programs and some hacks to break up the images into smaller subsets. I decided to write my own set of tools for processing the files recovered from data carving.

Data Carver Processors

The Data Carver Processors are a combination of Perl scripts and other programs that are designed to break up the recovered files into manageable chunks. As the script runs over the files, it will create a series of web pages with thumbnails and a second web page for each file that contains plug-in output like metadata, hashes, and etc. The scripts, for the most part, will not process damaged files. If a file is damaged, there will be no image for it on

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Dealing with PC Guardian's Encryption Plus Hard Drive (EPHD)

Dealing with EPHD, or PC Guardian's Encryption Plus is not too bad provided it has been setup correctly. By being setup correctly, I mean that the PC administrators have created an account that anyone can use to get past the hard drive encryption. This account and password needs to be treated just like the admin account. Only those people who need to know it, should have the userid and password.

On a side note: If your corporation has not implemented for your laptops and mobile devices, I have to ask why not? Hard drive encryption is much cheaper to implement then letting your corporate secrets and customer data out into the public.

Before We Begin

Before doing anything talk with your management and legal with regard to how they want you to proceed with imaging the encrypted devices. They may feel that this methodology is not right for them. The other aspect to be aware of is do you image the drive in its encrypted state and then use the

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Strings, Strings, Are Wonderful Things

One of the basics of doing forensics involves gathering the ASCII and Unicode strings in the file system and searching for keywords. Using Linux we can gather the strings for both ASCII and Unicode using the strings command.

To Gather the ASCII Strings

# strings -td /dev/sdb > sdb.ascii

Note: The -td in the above line tells strings to print the offset in decimal for the line.

To Gather the Unicode Strings

# strings -td -el /dev/sdb > sdb.unicode

Note: The -el option will have the strings command handle 16-bit little endian encoding. Strings can handle other types of encoding such as 32-bit big/little endian. See the man page on strings and the -e option.

Below is a sample output from the command:

192301896     
192301972 This field is deprecated. Deprecated components of Microsoft

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