Skypeex - additional comments

I've had some very good feedback about the Skypeex tool and I appreciate all your comments.

One or two have not really seen the point of the tool as there are plenty of Skype log viewers around such as from Nirsoft and Skypr. I will repeat what I posted on the LinkedIn discussion board.

"the Nirsoft tool, and others, are log viewers and this presupposes that you have access to the disk/logs. A covert live acquisition will often just take RAM and other volatile data, RAM may be taken before the plug is pulled only to discover that the disk is Full Disk Encrypted or that the logs are in a Truecrypt container. The user could even be using 'Portable Apps' Skype on a USB key which would mean no log files at all on the disk, however the data could still be in RAM.

This little tool is not meant to be a replacement for the excellent chat log viewers out there but provides a way of getting the data from RAM where circumstances dictate."

I'm working on an improved version where Strings isnt needed and hope to have that sorted in the next couple of weeks.

Skype Chat Carver from RAM - Skypeex

Well I was going to keep testing but it just seems to keep working, so here it is in version 0.5.

Download

I’ve been teaching my RAM analysis course for about a year now and enjoy working with Volatility and some other open source tools. I’ve been making use of Jeff Bryners cool little Python script (http://www.jeffbryner.com/code/pdgmail) to extract Gmail artifacts and was motivated to do the same for Skype chat and any other Skype stuff that might be hanging around in a RAM dump.

The only problem was that, although I’ve done a bit of programming in the past, Python was a long hissy thing you wouldn’t want to meet on a dark night. Having gone through the pain of programming ‘Hello, world’, simple Pokemon text games for my lad and tedious maths exercises, I’ve actually managed to produce something meaningful.

The idea is to extract Skype chat lines with their associated meta-data, which includes timestamps, the Skype names in the conversation and the author etc.

The complete Skype line in RAM starts with the magic value ‘INTO Messages” followed by column headers then the values of the chat line including the chat body.

This is very much work in progress but will simply do the following:-

1. Run Strings against your RAM dump
2. Run the Skypeex tool against the resulting Strings file
3. It will carve out all the Skype chat lines it can see as well as trying to find and extract all the Skype sessions and ‘orphan’ chats that have been created.

It’s interesting to note that the latter process even seems to find the ‘spam’ message sessions that you sometimes receive.

This has been tested on dump files from Windows XP2 and XP3 with Skype 3.8 through 4.2.
I don't currently have a Windows 7 box up and running, if anyone has one available please let me know.

Please do not hesitate to get in touch with ideas and improvements.

Usage:

There are 2 versions in the zip file.

skypeex.py is designed for use under Python 3.1.1 and above

skypeex26 is designed for use under Python 2.6

Due to changes with several commands between 2.6 and 3 they are not interchangeable, although the differences in this code are only in the input and print lines.
For best testing results, have several Skype IM chats with friends and then image your RAM. On a windows box, use any tool to grab RAM (tested on Win XP SP2/3):

I recommend Win32dd (or Win64dd) from Matthieu Suiche - http://windd.msuiche.net/

Run strings against the RAM image (e.g. Windows version can be found in Helix distro)
example: strings c:\ramdump.dd > c:\stringsout.txt

On linux box do:
strings ramdump.dd > stringsout.txt

Script usage -
from command shell - python skypeex.py - then, when prompted, simply provide the path to the strings output file.

The output files will be written to the folder where the script is run from. The output is a CSV file with chats (incl headers) and a txt file with extracted skype sessions and carved orphan chats. Please expect many duplicates and some false positives.

In the CSV file the 'Timestamp' column is the date and time of the message in UNIX time. Sorting on this column gives you a timeline of messages. I'm writing a UNIX time decoder but it doesn't work yet.

The primary message content is in the 'body_xml' column.

Code:

The key elements of the code are:-

if "INTO Messages" in line:
def extract(text, sub1):
return text.split(sub1)[-1]
str2 = extract(line, 'VALUES (')

This searches for the magic value, strips out the rubbish and returns the comma delimited values we are interested in. This includes:-

Chatname – the initiator and recipient of the session
Timestamp – The time and data the message was sent in UNIX time
Author – the sender of the message
From_dispname – the screen name being used by the sender
Body_xml – the body of the message, can slip into the chat_msg column
GUID – session identifier

Next:

if "#" and "/$" in line:
outfile.write(line)
nxt = next(data)
outfile.write(nxt)

This time we look for the existence of the # and /$ characters in the same line. This refers to the pattern written to RAM of each Skype session, which looks like this:

#nfurneaux/$bennyboy1982;810b0fd9ef04db08

This shows the 2 persons in the Skype session with the first name being the initiator of the conversation. I’m still trying to figure out the hex value at the end, but it seems to be a GUID session number, any ideas let me know.

Sometimes we recover session line like the following:

#bennyboy/$nfurneaux;9fa7c85b71354392Jd1bbennyboy1982Ben Brown
#andyw/$nfurneaux;9fa7c85b71354392Jd1TnfurneauxNick Furneaux

We are able to see the actual Skype name as well as the screen name being used during the session. The cool thing is that we also grab the next line with often includes actual chat associated with the recovered session. Hence we capture:-

#bennyboy/$nfurneaux;8f915423c984767aJ[VonfurneauxNick Furneaux
ok quite close
# bennyboy /$nfurneaux;8f915423c984767aJ[bennyboy Ben Brown
Aug 23
# bennyboy /$nfurneaux;8f915423c984767aJ[VQnfurneauxNick Furneaux
when are you presenting at HTCIA
# bennyboy /$nfurneaux;8f915423c984767aJ[bennyboy Ben Brown

Interestingly this conversation is carved in reverse. We can ascertain that bennyboy started the conversation but see the sender in the second part of the session line, followed by the chat.

I've never released a tool to the community before so be kind! Let me know how you get on.
Nick Furneaux

Download

Unfit and unblogged!

Im just preparing to release a Skype RAM carver written in Python and I thought that my blog would be the best place to put it. However, I just checked it to make sure I remembered how to log in and noticed that my last blog was in Oct. This is a coincidence as Oct was the last time I went for a run! I was thinking that there was no correlation but actually, moving house, traveling all over the place and a very busy work 6 months has contributed to both.

Yesterday I went out with my lad and ran for 2.5 miles, including loads of up hill and was pretty surprised at my retained fitness, which is good, however my blogging looks in much worse shape.

It doesn't help that the eponymous Happy Monkey is regularly blogging fabulously funny and insightful ditties that anything I do will be put to shame. However, watch this space for a free, and rather cool, Skype Chat RAM Carver.

Although I quite like this blogging lark, you will notice from the total lack of activity in recent months that I’m not very good at it. Fact of the matter is that I’ve been extremely busy, which I guess in the current climate I should be thankful for. Computer Forensics is a good career choice in a recession as, simply put, there are always bad people. In fact there is some evidence that white collar crime (and today that almost always involves computers) is on the rise as people worry about jobs, mortgages etc and when an opportunity to pilfer away a quick buck is found, many will succumb.

I’m writing this on a train to the Midlands where I’m helping a Bank improve its analysis of Malware written specifically to target its customers. This too is on the rise with phishing attacks commonplace. The problem with Malware written specifically for a task is that the AV products often don’t have a signature for it and hence it renders itself fairly invisible even from the ‘Heuristic’ scanners. To counter this it seems that the AV companies are lowering the bar, almost every time I write a script or compile a new piece of code, Kaspersky or AVG or McAfee scream that its Root Ware, or a Trojan or something equally nasty.

If you download virtually any of the fabulously useful tools from Nirsoft (www.nirsoft.com) such as their password recovery, USB key parser or Wifi tool and, wham, ‘It’s a virus!!’. No its not. Cain and Able password recovery tool recently started triggering an alert, Nessus fires an alert….what is going on. It feels at the moment that any software tool not in their database is automatically a Trojan come to steal your car, wallet and way of life.

Anyhow, rant aside, there has to be a better way of analysing Malware and I think RAM is the answer. Nothing can hide in RAM, processes hidden from the OS can be uncovered in RAM. Many tools do a process called List Walking to discover processes running in live RAM or a RAM dump however manipulating the DKOM object can render a process out of the ‘flow’ and essentially invisible from the OS or from list walking programs. Psscan2 in the volatility suite overcomes this by scanning the dump file for process objects whether or not they are connected to others. Outputting this view in a dot format and opening in something like graphwiz provides a fantastic, clean view of the running processes and their threads. Simply invoke by:-

Python volatility psscan2 –d –f > output.dot

Analysing the process start times, thread and parents, exe path and other variables provides a very ‘quick win’ when searching for malware of any type.

This is a manual process and would be tricky to automate but very worthwhile to do if malware analysis is your business.

Few minutes til the train is due in so will speak later, hopefully sooner!

ACPO and RAM Analysis course

It’s been a busy few weeks which is why I haven’t had a chance to blog for a while. I had the opportunity to present at the ACPO Conference 2 weeks back which is always a good event, with friends and colleagues from many different Forces and Agencies. It is normally a chance for a late night drink but exhaustion from the past few weeks activities had me in bed by 11pm each night.

My brothers company, Bright Forensics, was exhibiting there and had e-fense’s Eric Smith on the stand. Eric is a very talented investigator and has a tremendous knowledge of the forensic world and marketplace. They were focusing on touting e-fenses’ Live Response key. This is a USB key designed for fast and easy acquisition of live and volatile data from a running machine. In my view it is the first tool that provides an ease of use capable of being used by a front line arresting officer. I know that this is a sensitive subject at the moment, but a plug and play device that will grab Internet History, RAM and other useful data, is a very interesting addition to an officers arsenal. Discuss ☺.

The buzz word of the conference was ‘Triage’. In simple terms the phrase is being used to suggest that we could use a device or software tool to ‘search’ a machine and include or exclude it from an investigation, hence shortening backlogs that exist in most HiTech Crime units . Umm. I have a real problem with the idea of triage in this situation. In a hospital or emergency setting triage is used to prioritise not exclude and I think this is where such tools could have a role. If you get 5 machines in for a CP case, prioritising the machines, perhaps quickly locating the one with the primary evidence could work fine. However, I think that we will struggle to never image or investigate those other drives. If I think as a defence expert I may suggest that although there was a large amount of evidence on one drive, evidence existing on the ‘sons’ or ‘lodgers’ computer could lend credence to the fact that someone else used the computer belonging to the accused. I appreciate this is somewhat simplistic and perhaps the initial data might make the chap stick his hand up, but I’m sure that you can still see my concern.

Last week I taught my first Advanced Live Forensics course with a particular focus on RAM analysis. I don’t mean to blow my own trumpet but I think it was a resounding success. A chap from one of the UK Counter-Terrorism units suggested that it should be required learning for all computer forensic people and another was impressed by what he called the ‘first new computer forensic discipline since the advent of disk forensics’. Overall, I was chuffed. Obviously this is rapidly turning into an advertisement which I apologise for but if you would like to come then you can find dates on the www.csitraining.co.uk website!

ACPO and RAM Analysis course

It’s been a busy few weeks which is why I haven’t had a chance to blog for a while. I had the opportunity to present at the ACPO Conference 2 weeks back which is always a good event, with friends and colleagues from many different Forces and Agencies. It is normally a chance for a late night drink but exhaustion from the past few weeks activities had me in bed by 11pm each night.

My brothers company, Bright Forensics, was exhibiting there and had e-fense’s Eric Smith on the stand. Eric is a very talented investigator and has a tremendous knowledge of the forensic world and marketplace. They were focusing on touting e-fenses’ Live Response key. This is a USB key designed for fast and easy acquisition of live and volatile data from a running machine. In my view it is the first tool that provides an ease of use capable of being used by a front line arresting officer. I know that this is a sensitive subject at the moment, but a plug and play device that will grab Internet History, RAM and other useful data, is a very interesting addition to an officers arsenal. Discuss ☺.

The buzz word of the conference was ‘Triage’. In simple terms the phrase is being used to suggest that we could use a device or software tool to ‘search’ a machine and include or exclude it from an investigation, hence shortening backlogs that exist in most HiTech Crime units . Umm. I have a real problem with the idea of triage in this situation. In a hospital or emergency setting triage is used to prioritise not exclude and I think this is where such tools could have a role. If you get 5 machines in for a CP case, prioritising the machines, perhaps quickly locating the one with the primary evidence could work fine. However, I think that we will struggle to never image or investigate those other drives. If I think as a defence expert I may suggest that although there was a large amount of evidence on one drive, evidence existing on the ‘sons’ or ‘lodgers’ computer could lend credence to the fact that someone else used the computer belonging to the accused. I appreciate this is somewhat simplistic and perhaps the initial data might make the chap stick his hand up, but I’m sure that you can still see my concern.

Last week I taught my first Advanced Live Forensics course with a particular focus on RAM analysis. I don’t mean to blow my own trumpet but I think it was a resounding success. A chap from one of the UK Counter-Terrorism units suggested that it should be required learning for all computer forensic people and another was impressed by what he called the ‘first new computer forensic discipline since the advent of disk forensics’. Overall, I was chuffed. Obviously this is rapidly turning into an advertisement which I apologise for but if you would like to come then you can find dates on the www.csitraining.co.uk website!

Imaging Windows 7 Live

I've been spending some time working with Matt Blackband today on issues surrounding imaging Windows 7 disks and RAM. I've got a copy of Windows 7 32bit RC1 installed under VM Fusion with 2 Processors and 2 Gig of RAM allotted to it.

Before I start I just want to point out that although I have quite a bit to do with e-fense on a day to day basis including teaching the use of Helix 2.0, I do not make anything out of the new Helix Pro. This bit of research was just myself and Matt wanting to see whether it worked well under Windows 7 and compared to Helix 2.0. This is NOT an infomercial!

Although there has been alot of talk about exFAT and its uses, Windows 7 installs with NTFS as default and installed very quickly indeed. There have been some concerns and questions over whether our current typical live forensic tools would be able to successfully run and acquire drives and RAM. As Helix is a personal favourite tool and one that I teach, I focused my attention on that.

I loaded the latest Beta 2 version of Helix Pro (Should be released soon) which loaded quickly and successfully. Helix Pro saw the connected drives and partitions and also correctly reported the RAM size. Running the Helix RAM acquisition I was able to acquire 2 Gig of RAM, writing to a shared drive on the host MAC in a little over 2 minutes which is very good indeed. I was then able to successfully run Strings and Foremost to extract text data and carve files respectively. As expected Volatility refused to run and we wait to see if a Vista/7 update is forthcoming?

Disk imaging also worked correctly as expected for making both a RAW and an Encase 6 image, also creating disk and imaging information and checksum PDF's.

One of my favourite aspects of Helix Pro is its lightening fast volatile data acquisition. I was a little dubious that it would work under 7, but work it did, finishing in less than 20 secs and producing a 96 page report! Enjoy reading that!

Helix 2.0, the remaining free offering, as expected, did not fare as well. The GUI fires up OK but you are unable to trigger a command shell from the GUI as no Windows 7 shell exists on the disk, however browsing to /IR/Vista, and opening a Vista cmd file directly and then running cmdenv, did provide a usable shell which enabled me to run binaries on the disk.

System Information worked correctly reporting Owner, Network and Logical disks.

As expected the GUI would not image RAM or Disks although extracting MDD from /IR/RAM to a USB key and running it, successfully imaged the RAM in a little under a minute to the local disk (not recommended in the real world :)).

After some down and dirty testing today it is good to see that Helix Pro is up to the task of working with 7 which I guess makes it a £200 tool worth having in your toolkit. Of course, it will be interesting to see the take up of 7 after the lack-lustre reaction to Vista, but I have to say, even as a hard and fast Mac user, its not too bad. It installed very quickly and just worked out of the box. The interface is clean and simple and programs pop up nice a fast. Could this be a 'good' version of Windows? Time will tell. More research to be done.