Forensic Discovery

Ben Rothke writes "When most people think of forensics, television shows like Quincy and CSI come to mind. Where such shows deviate from reality is the unrealistic speed at which the actors are able to identify, apprehend and prosecute the perpetrators. In the real world, (unlike television, where the crime must be solved by the end of the family hour), crimes are solved with slow, deliberate and methodical steps. The prodigious incidence of digital crime has elevated computer forensics to a critical role within the field of information security. The focus of computer forensics is twofold: first is the attempt to determine whether a breach has occurred and to stop the perpetrator; second is prosecution of the offender, if the breach was a criminal activity." Read on for Rothke's review of Forensic Discovery. Forensic Discovery author Dan Farmer & Wietse Venema pages 198 publisher Addison Wesley Professional rating 10 reviewer Ben Rothke ISBN 020163497X summary Forensic Discovery overview

Security luminaries Dan Farmer and Wietse Venema wrote one of the first vulnerability scanners (SATAN) almost 10 years ago; SATAN was the precursor to ISS Scanner, Retina and nmap. Venema wrote such well-known security applications as the TCP Wrapper program and the Postfix mail server. Farmer and Venema's new book Forensic Discovery is a valuable book that grounds a computer-savvy reader in the world of digital forensics.

An image of a pipe by artist René Magritte is on the cover with the caption Ceci nest pas une pipe. ("This is not a Pipe.") The picture demonstrates that an object exists on many planes; the simple recognition of the picture initiates the belief that we are seeing something, but it is only known in representation. Surrealist painting and digital forensics coalesce in that the digital forensic investigator must think broadly and unconventionally in order to reconstruct an incident, all the time keeping in mind that often what initially seems obvious is neither real nor correct.

The material in the book is an outgrowth of a one-time seminar the authors gave in 1999 on digital forensics and analysis. At the seminar, Farmer and Venema rolled out The Coroner's Toolkit (TCT), a collection of tools for gathering and analyzing forensic data on a Unix system. TCT is heavily referenced throughout the book.

The book initially seems thin, at just 198 pages, but there is no filler and the information is presented in a fast and furious manner. Part one of the book comprises 35 pages and is an introduction to the foundations of digital forensics and what to look for in an digital investigation.

Part two (chapters 3-6) is the nucleus of the book, which quickly gets into low-level details about file systems and operating system environments. While other forensics books focus exclusively on the discovery and gathering of data; Forensic Discovery adds needed insight on how to judge the trustworthiness of the observation and the data itself. Again, the idea is that not everything is as obvious as it may initially seem. An effective investigation often requires intense analysis, where meaningful conclusions take time.

Chapter 4, "File System Analysis," notes that while computers have significantly evolved since their inception, little has changed in last 30 years in the way that file systems actually handle data.

Chapter 5, "Systems and Subversion," is particularly interesting as it deals with system startup and shutdown, from a forensics perspective. The chapter shows that there are thousands of possible opportunities to subvert the integrity of a system without directly changing a file during startup and shutdown. A crucial decision that must be made during an incident is whether to shut down the system or let it remain on-line. There are advantages and disadvantages to each approach, and the book details them.

Part three (chapters 7-8) is about the persistence of deleted file information. The authors' research reveals that data can be quite resistant to destruction. The book shows that a huge amount of data and metadata can survive intended deletion as well as accidental damage.

Forensic Discovery is unusual in that other books on forensics are often nothing more than checklists and step-by-step instructions on what to do during an incident. Forensic Discovery provides a broad framework on the nature of data and how it can be recovered for forensic purposes. By understanding the underlying operating system, the act of analyzing and dealing with a security breach becomes much easier.

The book's target reader is anyone who wants to deepen his understanding of how computer systems work, as well as anyone who is likely to become involved with the technical aspects of computer intrusion or system analysis. The topics are too advanced, to make it the right book for the novice system administrator. For the technical reader, though, Forensic Discovery is one of the best computer security books published in the last year. The value of the information is immense, and the extensive experience that the authors bring is unmatched.

You can purchase Forensic Discovery from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

Computer forensics

[Anonymous Coward]

I met a young, single woman who did computer forensics for the police. She told me over dinner that while she thought her work was important, it caused her a lot of stress in her life. She said there were many times where she recovered images from the computer of a sex criminal that were really indiscribable.

She was really good looking and had a body that you normally don't find on a girl geek. But, man, I wasn't about to start dating some chick who comes home from work sobbing from prowling through gigabyes to violent sexual jpegs and avis. I guess that's why someone so damn good looking and smart was still single...

Re:That is why CSI sucks

[severoon]

I especially hate it when (this seems to predominate on CSI, but I've seen it on other shows as well) they "digitally enhance" security camera video to identify an attacker, read a license plate, etc. Usually, I can overlook it for the sake of the plotline every now and again. But, the final straw came for me a few weeks ago on CSI when they had an ATM security cam and the pulled a reflection off of the pupil of the third person in line and enhanced it to ID the criminal (second in line) who was facing away from the camera. They literally took a single grey pixel from the video and "enhanced" it to a beautifully rendered, studio-lit 8"x10" black and white portrait of the criminal.

And, oh yea, if you put deer feces into an NMR, it's not going to spit out a graph with a bunch of peaks on it and print below the graph: "deer feces". On the other hand, I'm not sure which is worse...when they do that with the NMR, or when they NMR identifies 50 compounds in a sample, all with names like "n-methyl hydride deoxynitrate", and the CSI goes, "Oh, yea, those are the major components of plumber's grease that was used between 1970 and 1978 in the Western United States." They might as well have the NMR spit out a graph with a caption: "The bus driver did it! The motorcyclist was only his *accomplice*."

Then, of course, there's the small issue of unlimited budget. If real CSIs solved crimes like they do on TV, they'd be spending somewhere between $15M and $50M per case. :-)

In all seriousness...

[Anonymous Coward]

Sounds like she needs some consoling.

Well, it was that "some" in "some consoling" that I wasn't sure about. How much? She's telling me on the first date that she's under tremendous stress. I appreciate her honesty and respect her for that but I suspect that if she feels the need to divulge that on a first date, the level of consoling is likely to be more than "some". That's what I was worried about. To be dating a girl with a face and a body like that who knows her way around computers like a pro and who is doing a job that is clearly a service to mankind sounds like a geek's wildest dreams come true. But therein lies the problem: this is the kind of girl who most of us would fall head-over-heels for. I was afraid of getting really wrapped up in her and then having to endure of heartache of having her crying in my arms once a week or more. Or having her push me away in bed because she had seen something at work that had turned her off of sex for the next two weeks. You can call me an ass or a dumbshit but seriously think about it for a moment. This was going to be a major emotional roller-coaster for me.

I'm reminded of some poor sap here on slashdot who was telling us what it's really like to have a nympho girlfriend. It sounds great until you are presented with the reality of the situation, namely, that she absolutely needed sex every time he put his arm around her. Look, I still think that woman I dated was very desirable on many, many levels but I also think I did the right thing by stopping that relationship before I got sucked into her work as well.

Re:Computer Forensics = FRAUD (fbi puts files in)

[DoctorMabuse]

This poster is totally incorrect. I have served as a computer forensic expert in both civil and criminal cases, and can tell you this poster does not understand the process. For example, the prosection and defense may find an impartial examiner or use two examiners and make two copies of the seized disk or disks. Forensic tools with copy capabilities such as EnCase will make a bit-for-bit copy (including non-allocated sectors, file slack space, etc) of the disks and perform an MD5 checksum over the contents.

I now perform my work on the copy. Any results I obtain can be demonstrated in court, as can the fact that the MD5 hash is the same and that my disk is still identical to the other party's copy.

If chain of evidence is maintained, I should get the disk as it was when it was seized. Once I have it and copy it, it is effectively tamperproof, because of two persons each having a copy, the MD5 hash, additional checksums built into EnCase copy structures AND the fact that we can always recompare our copy to the original to determine it is still bit for bit.

The scientific validity of computer forensic methods can be subjected to a Frye or Daubert hearing, where scientific experts can defend the method. EnCase has already been through these hearings and no credible argument has been advanced against its validity.

If you competent defense counsel or civil counsel, this should not be a concern.