Computer Forensics

Craig Maloney writes "Many Slashdot readers know how to secure a network, and many know how to determine if a security breach has taken place. Fewer readers, though, would know how to handle a security breach if corporate assets were involved. How would you cooperate with law enforcement when a crime has been committed on a computer?" For more questions, and the rest of Maloney's review of Warren G. Kruse II and Jay G. Heiser's Computer Forensics, read on below. Computer Forensics author Warren G. Kruse II and Jay G. Heiser pages 392 publisher Addison Wesley rating 8/10 reviewer Craig Maloney ISBN 0201707195 summary A good reference for what to do when computer crime happens

How do you get the evidence off of a computer, ensuring that it's capable of withstanding a defense lawyer's scrutiny? Maybe you would just unplug the machine and put it in storage awaiting a detective's arrival, but is that what we should do? What if the evidence is on a production server that can't be simply unplugged and put into storage? What if that evidence is slowly being erased as files are created and deleted on that server? How do you help build the case against a computer criminal? Hopefully you'll never have to worry about computer crime in your home or workplace but if you do have to worry, Computer Forensics will be an asset to your part of the investigation.

Who is this book for? Computer crime isn't simple -- it can range from damage done by simple script kiddies to corporate espionage by disgruntled employees, as well as sophisticated, multi-homed attacks by skilled crackers. Computer Forensics tries hard to cover a lot of these areas. The book includes a chapter dealing with laptop hardware, as well as ones on data hiding and encryption, and further chapters on putting evidence together and dealing with law enforcement. While these topics may be of interest to the Slashdot crowd, Computer Forensics focuses more on broad topics of interest to computer detectives faced with getting up to speed quickly with computer crimes and computer evidence gathering.

Several chapters are downright boring for anyone who has a modicum of computer experience. Finding out where e-mail is stored on Windows and Linux machines, or understanding what a root-kit is and what it does will be pedestrian for many readers. Nestled away between the necessary-but-pedestrian topics, though, are some very useful tools. The authors use netcat with tar to copy files between machines without disturbing the modification times (something I would never have thought to use). Novice users will find a wealth of tools and examples in these chapters. The tools used in the book tend toward open source and free tools, and rely heavily on Linux as the Swiss Army knife for handling file systems and files without disturbing them. Any reader should be able to put together a decent set of tools from this book.

Making it all work

Putting together a good forensic kit is all fine and good, but making sure your evidence holds up to the scrutiny of some high-powered, high-priced defense lawyer is much more important. The last chapter of Computer Forensics gives a brief introduction to the criminal justice system. The authors touch on notifying law enforcement agencies, search warrants, probable cause, interviews, subpoenas, dollar loss guidelines, and testifying as an expert witness, among other legal topics. The appendices of the book have checklists, flowcharts, and an incident report form to aid investigation and evidence gathering. These are invaluable resources for the system administrator of any public machine who needs to deal with law enforcement.

Conclusion Thinking about dealing with courts and law enforcement may not be at the forefront of any administrator's job, but it is a reality any administrator needs to think of and be aware of. Computer Forensics will at least make administrators more aware of what their legal options are, and of the form in which gathered forensic data needs to be presented as evidence. Computer detectives will find a good, if not rudimentary example of what to look for when investigating a computer crime scene. This may not be the most comprehensive book on the subject of computer crime, but it will point you in the right direction to help investigate it should it ever happen to you.

You can purchase Computer Forensics 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

SecurityFocus

[ProfaneBaby]

The security focus mailing list dedicated to forensics is also good lurking, for those interested...

http://archives.neohapsis.com/archives/sf/forensic s/

Enterprise file forensics

[Anonymous Coward]

We use Dynacomm i:scan in our enterprise and it basically does all the forensic work for us. Kinda spooky the things it can report and notify on.

Re:Enterprise file forensics

[ikewillis]

For the rest of us there's always Wietse Venema's tool, The Coroner's Toolkit

On FreeBSD, it's all about mtree...

Re:Enterprise file forensics

[LordDracula]

If so, do you know if the results from these forensics tools are useful and/or admissible in court?

Admissibility is not so much tied to the specific tools (though this can be an issue; more on this later) used, but the methodology used.

DISCLAIMER: I am not by any means a forensics expert, but I am doing an independent study in computer forensics in college.

That said, many of the standard *nix tools are, in fact, acceptable for court use. For example, it is extremely unlikely that you will have a challenge presented in a courtroom questioning the integrity of your forensic duplications if you used 'dd' to make the images. At least, not on technical grounds--failure to document everything correctly and completely could wind up causing inadmissibility.

I'd strongly recommend Incident Response & Computer Forensics by Mandia and Prosise (of Foundstone, Inc.). This book has a LOT of technical information, and covers the aspects of evidence handling, documentation, etc. very well.

Looking at some of the tools listed in the Knoppix STD, I can say that many of them (like fatback, foremost, dcfldd, and cryptcat) are recommended tools in the Mandia/Prosise book. I've used each of these, and they are all definitely useful. If you're doing work that must stand up in court, however, make sure you document everything you do, and never, never write anything to your suspect drive! Doing so will not only risk losing evidence, but also invalidate the entire drive as evidence. All forensic analysis should be done on either a qualified forensic duplicate or full forensic duplicate.

Outside the U.S.

[Bingo Foo]

In other countries, this book is titled, How to Avoid a Forensic Data Trail on Computers You Compromise.

Re:Outside the U.S.

[donscarletti]

Many mods will moderate funny things as one of the catagories starting with 'I' because funny doesn't give any karma. If something is moderated as funny and is later moderated back down again, the poster could actually loose karma because of it so many mods think it is unfair.

Time sync all your computers

[uid100]

OS level Forensics are much easier if all your computers are set to the same time.

There is no (good) exuse for not at least NTP'ing all your servers.

Re:Time sync all your computers

[Nonesuch]

There is no (good) exuse for not at least NTP'ing all your servers.

There used to be a good excuse -- recurring root holes in all common NTP implementations.

With OpenNTPD, this is no longer a valid excuse.

Crime On Computer ...

[foobsr]

when a crime has been committed on a computer?

Must be old mainframes then.

CC.

Forensic Security

[djrok212]

Many financial firms including the one where I work, have instituted internal forensic security policies to help limit corporate liability. In our case, we have caught and successfully prosecuted employees for pornography on corporate assets (including child pornography in one case.)

There are designated employees on the forensic team in each department who are responisble for witnessing the process and documenting the chain of custody for data and items.

We've invested in specific equipment, including network sniffers (other then those used by the network group), hard drive replicators, log books, and materials for collection and storage of evidence.

Everything has a chain of custody and is then turned over to the proper authorities.

As far as the law is concerned since the employee does not have a right or expectation of privacy when working on a corporate asset, everything we take is completely legal. As long as we mantain an effective chain of custody it will likely hold up on court.

Just my two cents. Your mileage may vary.

Cutting Loses

[fembots]

What if the evidence is on a production server that can't be simply unplugged and put into storage?

In my company, once a machine is compromised, it's offline and ghost image taken, no questions asked, even it's a live ecommerce site. You would rather putting up a "Unscheduled Outage" notice than inflicting more damages to the server/data.

It's like a 777 pilot asking if he should make an emergency landing due to a fire alarm, because there are 350 passengers onboard and we don't want to spoil their holiday.

Actually I think pilots do that, that's why we get to read blackbox transcript like

GPWS: "Whoop, whoop. Pull up. Whoop whoop. Pull up."
CA: "Don't worry we can make it."
GPWS: "Whoop, whoop. Pull -."

Been there, done that.

[rylin]

Recently, I was contacted by the local PD in regards to a huge number of stolen CCs being used from our IP-range (Internet Café).
After getting a list of specific timestamps (along with IP-addresses), I was able to figure out who the culprit was.
That said, the man-hours I put into the whole thing seem to have been for nothing.
The PD won't do jack shit - too little resources, they say - which is why I find it funny that they can't even send a unit to pick up the frauders when they're actually on-site (yet they can be seen parading the streets, looking for minors consuming alcohol).

Just because law enforcement want your help doesn't mean they'll do anything - even if you virtually hand them the crooks on a silver platter.
Then again, things might be different elsewhere.

Re:Been there, done that.

[HarveyBirdman]

Well, someone jacks my CC number, I'm on the hook for a max of $50.

A drunken minor behind the wheel of mom's Ford Excursion costs me far, far more than that should I encounter the illbred little monster on the road.

Hey, just presenting a contrarian view. Was it at least an interesting learning experience?

outdated?

[Boolio]

The publication date on the book linked is 2001. That makes this book three to four years old. While some of the information may be the same, there are quite a number of new tools and techniques out there. So some of this may be pretty outdated. I have yet to find a great book on system forensics. The best so far is the book "Know Your Enemy" buy contributors to the HoneyNey Project.

This is dangerous stuff to mess around with...

[Pacifix]

... like security, forensics is best left to those who really know what they're doing. The results of a forensics investigation can very often end up being part of a civil or criminal case and amature mistakes can get the case thrown out. Contaminating the data by not properly imaging it, not knowing where to find hidden data, or misinterpreting what is found are all very easy to do. Be very sure you have all your bases covered before selling yourself as a forensic investigator.

Re:This is dangerous stuff to mess around with...

[-strix-]

thats true. I tooke a computer forensics class at my school about a year and a half ago, it was a great class and this book was one of the ones we used. One of the main points our professor drove home was properly maintiaing a chain of evidence. This is something that would be second nature to a criminal justice major but is pretty foreign to someone in computer science. As far as being a forensic investigator, i would look for a GIAC Certified Forensic Analyst certifcation. I know that alot of people are dubious about how much stock they put in certifications but this is really a good one. To date there are only 124 people who have obtained this certification. more info about it here: http://www.giac.org/GCFA.php

An actual example of corporate breaches.

[pjbass]

I work at a large semiconductor company (not to name names, but a really big, US, SC-based one) that had a recently fired employee wreak havoc on one of the factories' databases as a result of his termination. Basically he used his not-yet-cancelled remote access, and deleted a critical DB. Now this isn't hacking in the sense of rooting a remote exploit, but it's malicious intent nonetheless on computer systems. It was obvious what happened (the factory stopped running), and very quickly we were able to track down the last few commands logged, where they came from, etc., etc. How it was handled was actually an FBI case. We turned it over to the security department at our company, and they worked with the FBI; we were asked questions by the men in black, and this person was eventually arrested and put away in a dark, dank hole.

Not sure if this is the norm, but I'd figure when corporations and expensive IP is involved, government-sanctioned agencies will be in the forefront of people investigating, IMHO.

The computer is the victim.

[eln]

Whenever you do work like this on computers, it's important to know that the computer is ultimately the victim here. Don't be too rough with it in trying to get information. It's important to get information back, but it's also very important to maintain the computer's well-being. Always ask before taking a look at the computer's hard drives. If the computer refuses, back off and try again another day. After being so traumatized, many computers will not feel comfortable letting you in right away. In some cases, gender may be an issue, so always use female-to-female or male-to-male data cables when attempting to access the computer's internal ports, as recently attacked computers may have more hostility toward opposite-gender pairings in interrogations.

Please, always make the computer your first priority, and be mindful that you do not damage it further in your rush to make an arrest.

Step 1

[Kallahar]

Step 1: Turn off the machine.
Step 2: Make a bit for bit copy of the drive (there are special devices that will ensure that NONE of the bits are changed).
Step 3: You can now run whatever forensics tools you want *on the copy*. The original has to be kept unchanged for it to be worth anything in court.

Make sure to never boot up the drive in question, a good criminal will have the drive auto-erase if it doesn't get a password in a certain amount of time, etc.

Re:Step 1

[towaz]

I would not just kill the machine yet either. As long as you document your findings and what you do to the system (with witnesses) you can do a few things first.

On the live system you can not trust anything so a cd or other media containing your tools statically compiled to investigate are needed.

you can use dd to make a bit for bit copy of ram, pipe this through netcat to your forensics box, or cryptcat is sensitive info is on the compromised machine.
A good idea would also be to calculate an md5 checksum for the image either side of the netcat pipe to verify its not messed up.

then run lsof to check what ports are open and by what applications and pull the plug out the wall on the compromised host.

then make sure boot priority in the bios does not boot the hdd in question and run knoppix or something like F.I.R.E and run md5 on the drive, pipe it to your machine with nc and then md5 that image.

I know i missed something but am on the phone so i guess will wait to get flammed :)

Transfering for forensics

[Kalak]

Rsync will do this simply and efficiently, plus it can resume transfers and also tunnel through ssh.

Also you can pipe dd through gzip/bzip2 and netcat to give you a loopback mountable, unmodifiable image that you can look at in case you want to grab the whole drive before putting it in the evidence locker.

Valve

[FiReaNGeL]

In the case of HL2 code theft, Valve got lucky; they just had to wait for the hacker's ego to blow out of proportion due to the massive coverage. He emailed them. Several times. He went to a meeting for an 'interview' for a 'job'. Thank god, most hackers(as in illicit network infiltration) / criminals eventually make mistakes. In this particular case, it was pure dumbness, however. Imagine the scene :

"Honey, you know the company that I (big F word, past tense) over, well, they're offering me a JOB!" "Great! When are we moving?"

Heh.
past /. coverage

How would you cooperate with law enforcement?

[RealAlaskan]

How would you cooperate with law enforcement when a crime has been committed on a computer?

Wouldn't that depend on your role in the crime, and your lawyer's advice?

WWYD? STFD, STFU, and DWYT.

[Tackhead]

> How would you cooperate with law enforcement when a crime has been committed on a computer?

I would do whatever the nice people with the guns told me to. Nothing more, and nothing less.

The guys with the guns are not my friends, but they're pretty nice to people who help them. The most helpful thing you can do for these people is to sit the fuck down, shut the fuck up, and to do what you're told.

Unless you're being paid to perform an investigation, getting good forensic data off that drive is not your responsibility. That's the responsibility of the friends of the guys with the guns. (Are you a friend? Easy to check! Is your paycheck signed by a big guy with a really big gun? If not, you are not one of their friends!)

Going further, getting data off the drive isn't your responsibility -- but not fucking up the chain of custody is your responsibility. If you fuck up the chain of custody, the guys with the guns will be very, very, very angry with you. (You do not want this to happen.)

So:
1) Do not make the people with guns angry.
2) Do not "help" the people with guns (even if you want to), because anything you do to "help" them runs the risk of making them angry.
3) STFD. STFU. DWYT.

Y'know how we geeks have hundreds of words to express the concept of "nontechnical person who is too clueless to be allowed anywhere near a computer"?

I'll bet cops have hundreds of words that translate to "civilian who is too clueless to be allowed anywhere near an ongoing investigation".

A 'thank you' from the SF forensics moderator...

[sczimme]

The security focus mailing list dedicated to forensics is also good lurking

I am the moderator of the SecurityFocus.com forensics list, and agree that it is a great resource. (Al Huger is listed in the info page as the moderator; he is actually the list owner.) The list is dedicated to discussion of technical forensics topics.

The SF forensics list archives are here. A general listing of SF mailing list archives is here. Those interested in subscribing to the forensics list (or other lists @SecurityFocus) can do so from the archive page.

Cheers!

Scott C. Zimmerman, CISSP