
Let's talk a little about this class before we get started.
These are just a few simple things you can do to create to create a beneficial training environment for yourself.
In this section you will be introduced to Apple File System time values and Apple Metadata Time values. It is important to understand the difference in order to explain findings.
It is always a good idea to see things from a user's point-of-view. It is important to understand what a user sees and does not see natively on a Mac. This may come into play later during artifact time interpretation. Let's take a closer look now.
Next up Apple Timestamps and how to pull out the values using the Terminal. I use this a lot day to day and I'm sure you will find it useful not only for time values but as a method to access the different types of metadata associated with a file.
Latency may be a problem. We are going to be experimenting with files which means OS X is going to have to keep updating the metadata on our test files. This section is a brief discussion on the latency issues you should be aware of.
This is our first date and time validation test. To get a base line we will create a new file and look at the time properties.
Steps:
1. Open Textedit.app
2. Create a new RTF document and add some text
3. Save it to your Desktop
4. Open Terminal.app and run MDLS against it
5. Examine the file's time properties and note the values in your worksheet
Our next validation test will explore the changes that are made when a file is edited.
Steps:
1. Edit the test file by adding text to it using Textedit.app
2. Save the file and close it
3. Open Terminal.app and run MDLS against it
4. Examine the file's time properties and note the values in your worksheet, note the differences between this file's time properties and the file properties of the new file we created
In this test we are simply going to access our test file.
1. Open the test file using Textedit.app
2. Do not make any changes, just close it
3. Open Terminal.app and run MDLS against it
4. Examine the file's time properties and note the values in your worksheet, note which time properties have changed and the new values
In this exercise we will move the file to a different location on the same volume and see the results.
1. Create a new folder on your Desktop
2. Drag and drop the test file into the new folder
3. Open Terminal.app and run MDLS against it
4. Examine the file's time properties and note the values in your worksheet
In this exercise we will move the file to a different location on a DIFFERENT volume and see the results.
1. Create a new folder on and HFS formatted USB drive
2. Drag and drop the test file into the new folder
3. Open Terminal.app and run MDLS against it
4. Examine the file's time properties and note the values in your worksheet
How downloading a file affects date and time stamps if often a topic in a computer forensic exam. Let's see what happens with this in OS X.
1. Download a larger file such a the Paladin ISO image available at Sumuri.com (this way you get the added benefit of a free computer forensic tool as part of the test)
2. Note the time the file download begins and ends
3. Open Terminal.app and run MDLS against it
4. Examine the file's time properties and note the values in your worksheet
Ah yes, file deletion. If I only had a bitcoin for every time I was asked if I could tell when a file was deleted...
Since this topic comes up a lot let's do a validation test to see what time artifacts we get on OS X.
1. Deleted the test file from the folder on your Desktop by dragging it to the Trash
2. Open your Trash folder
3. Open Terminal.app and run MDLS against it
4. Examine the file's time properties and note the values in your worksheet
Understanding OS X dates and times and knowing how to interpret them through validation testing will definitely aid you when conducting Mac exams. Are you ready for the next step? Timelines! This is where this should ultimately lead you to. The following is just my thoughts on how to bring your Mac exams to the next level by incorporating both time artifact analysis and building timelines.
I hope you enjoyed the class and feel more confident in dealing with OS X times. Here are some remaining thoughts I have about the topic and Mac exams.
Check out other classes at http://sumuri.com/training/surviving-digital-forensics/
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Welcome to the Surviving Digital Forensics series. This class is focused on helping you get a better understanding of OS X Time Stamps and to become a better Mac examiner.
As with previous SDF classes you will learn by doing. The class begins with a brief overview of OS X time - as Apple sees it - then we will get into a number of validation exercises to see how user activity really affects Apple time stamps. Learning is hands on and we will use applications already installed on your Mac to do so.
Expert and novice Mac examiners alike will gain from this class. Since we are doing it the SDF way we are going to teach you real computer forensic skills that you can apply to all versions of OS X. Therefore you are not just going to learn about OS X timestamps but learn a method you can use to answer many date and time questions that may come up in the future.
Class Outline
1. Introduction and Welcome to the SDF series
2. What this class is all about
3. How to get the most of this class
4. The finer points of OS X dates and times
5. Time from a User's point-of-view
6. Apple metadata timestamps & the MDLS command
7. Latency issues
8. Validation Exercise: New file
9. Validation Exercise: Modified file
10. Validation Exercise: Moving file within same volume
11. Validation Exercise: Moving file to a different volume
12. Validation Exercise: Accessing a file
13. Validation Exercise: Downloading a file
14. Validation Exercise: Deleting a file
15. Summary of findings
16. Thoughts on time attribute artifacts
17. Conclusion & final thoughts