Wednesday, June 17, 2009

Active Directory Snapshots

With Vista, Microsoft finally made proper use of Volume Shadow Copy and the Volume Shadow Copy Service. A lot of great work was done to help others use this during analysis. Server 2008 continues this model but it applies it to Active Directory. Sounds cool eh?

First off, let me say that this is well known to sysadmins, but I'm fairly certain it's not well known in this part of the industry. I've not seen it discussed on any list or forum I pay attention to at least.

For background - Read these pages here and here...I'll wait.

And now, go read this page here....I'll wait for you again.

So, now that you've read about creating Active Directory Snapshots and how to mount a VHD file in windows, let's discuss it.

When performing incident response in an Active Directory Environment, you're most likely going to want to look at a domain controller, especially if the domain controller is compromised, or there is something funky happening in the directory itself. Any self respecting sysadmin is going to have a regular system state backup of the domain controller. This is done so restores can occur if objects are inadvertently deleted, and also as a good practice. In server 2008, this backup is stored as a .VHD file. In a response scenario involving AD, we want to maintain our methodology of not modifying the system any more than we have to, so, we don't want to work on a live copy of Active Directory, we want to work from a snapshot of it.
Here's a pseudo scenario.

A compromise is believed to have occured in Active Directory.
Logging was disabled by the attacker on the domain controller, or the attacker covered his tracks in the logs.
You have been tasked with figuring out what was changed.
You have a recent system state backup.
You mount the system state backup and recover the AD core files.
You create an Active Directory Snapshot.
You load up Sysinternals Active Directory Explorer
You load the snapshot and the AD core files and Diff them in AD explorer.
You now have a smaller dataset to work with and you have a point in time diff of "what changed".

I'll be putting this together in a more formal manner..but I wanted to throw this out there for anyone that deals in Active Directory Compromises, especially with server 2008 domain controllers.


Keydet89 said...

You mount the system state backup and recover the AD core files.

Where does this activity occur? On the domain controller, or in your lab?

hogfly said...

That part is done in a lab on a Vista or more recent windows OS (7 or 2008)