Friday, February 19, 2010

Fun Analysis Stuff

Event Log Analysis
Here's another one for all of you out there doing Event Log Analysis. I installed Office 2007 (ie, version 12) on an XP system, and now I have two new .evt files...Microsoft Office Sessions and Microsoft Office Diagnostics. The Microsoft Office Sessions Event Log really seems promising...most of the events are ID 7000 or 7003 (session terminated unexpectedly). The ID 7000 events include how long the session was up, and how long it was active. While the event record doesn't appear to include a specific username or SID, this information can be correlated to Registry data...UserAssist, RecentDocs, application MRUs, tie the session to a specific user.

As we've seen before, Event Log records can be very useful...sorting them based on record number may show us that the system clock had been manipulated in some way. Another is to show activity on a system during a specific time frame.

Timeline Analysis
Speaking of Event Log records, an interesting and useful way to determine if the system clock had been set back is to sort Event Log records by event record number and observe the times...for each sequential record number, does the generated time for the record increment accordingly?

Another way to check for this (on XP) via the Event Log is to look for event ID 520, with a source of "Security". This event indicates the system time was successfully changed, and includes such information as the PID and name of the process responsible for the change, as well as the old system time (prior to the change) and the new time. An excellent resource and example of this is Lance's first practical.

Now, does event ID 520 necessarily mean that the user changed the system time? By itself, no, it doesn't. In fact, if you create a timeline using the image Lance provided in his first practical, incorporating the Event Logs, you'll see where event ID 520 is in close association with an event ID 35, with a source of W32Time...the system time was automatically updated by the W32Time service! You'll also find a number of instances where the system time was updated via other means. I'll leave it as an exercise for the reader to determine that other means.

An interesting side-effect of creating a timeline using multiple sources is that it provides us with event context. Historically, timelines have consisted of primarily file system metadata, and as such, did not give us a particularly clear picture of what was going on on the system when, say, a file was accessed or modified. Who was logged in, and from where? Was a user logged in? Was someone logged in via RDP? Was the file change a result of someone running a remote management tool such as PSExec, or perhaps due to something else entirely?

It's been a while since Cory Altheide and I published a paper on tracking USB removable storage devices on Windows systems. Recently, Cory asked me about web cams, and I started looking around to see what I could find out about these devices. As you might think, Windows stores a LOT of information about devices that have been connected to it...and with USB ports, and so many devices coming with USB cables, it just makes sense to connect them to your computer for updates, etc.

Now you may be wondering...who cares? Someone has a web what? Well, if you're law enforcement, you might be interested to know if a web cam, or a digital camera, or a cell phone...pretty much anything capable of taking or storing pictures...had been connected to the system. Or if there's an issue of communications, and you know the application (Skype, NetMeeting, etc.), then knowing that there was a web cam attached might be of interest. I'm thinking that having device information would be useful when dealing with pictures (EXIF data), as well as looking at different aspects of the use of applications such as Skype...did the user send info as an IM, or via video chat, etc.?

Interestingly, I have access to a Dell Latitude with a built-in web cam, and I took a couple of pictures with the software native to Windows XP...the pictures were placed in the "All Users" profile.

Speaking of taking pictures, got nannycam? Microsoft PowerToys for XP includes a Webcam Timershot application.

If you don't have a copy of the paper that Cory and I wrote, there's another one available here

Addendum: Volume Shadow Copies
Much like System Restore Points, you can't say enough about accessing files in Volume Shadow Copies...I'm sure that a lot of it bears repeating. Continually. Like from the sausage factory.

1 comment:

DC1743 said...

Thanks for the link to Forensics from the sausage factory. I had not realised that performing a hash analysis had been widely discussed or that the flaws in the imaging technique with regards to unallocated clusters had been commented on either. I also thought it would be helpful to look at the issues particular from the perspective of some of the less experienced Encase users.