Tuesday, October 29, 2013

Daily Blog #128: Detecting Fraud Sunday Funday 10/27/13 Part 1 - Time Changes

Hello Reader,
           Let's talk about system clock changes which is one of the areas not covered by this weeks Sunday Funday winning answer. Often times when creating fraudulent documents a suspect will change the date of the system in order to make the document appear to be generated at an earlier time. If you've done these cases on Windows XP you've probably read Steve Bunting's old blog regarding this, http://www.stevebunting.org/udpd4n6/forensics/timechange.htm. However the event ids and sources have changed since XP and since this challenge focuses on Windows 7 I thought it would be useful to show what clock changes now look like.

Windows 7 has a lot more logging turned on by default, as such clock time change events are logged. The entry will be found in the 'Security' event log and the source will be 'Microsoft Windows security auditing'. The task category is 'Security State Change' and the Event ID is 4616. Here is an example:

You can see that the event records the previous and new times, in this case my clock was 9 minutes behind and I set it forward. If the clock were to be changed back you would see the new time be earlier than the previous time.

If you wanted to quickly determine if a user had changed the system clock recently this is the best place to quick filter for Event ID 4616. The security log for a workstation on my system goes back two months and there would be additional copies of it in the shadow copies and possible freesspace if you can recover event log entries from freespace.

So that is a pretty simple way to detect when the system clock for the entire system is changed, pretty easy huh? Tomorrow we will going into individual files timestamps being altered.