Due to the increased number of cases of cyber-crimes and intrusions, along with the storage capacity of hard disks and devices, it was necessary to extend the techniques of computer forensics, currently works consist in collection and analysis of static data stored hard drives, seeking to acquire evidence related to the occurrence of malicious activities in computer systems after its occurrence.
With the evolution of technological resources and the popularity of the Internet, it has become impractical to maintain only the traditional approach, due to the large volume of information to be analyzed and the growth of digital attacks. In this context, the analysis of data stored in volatile memory comes up with new techniques, it is necessary to check the processes that were running, established connections, or even access keys encrypted volumes, without causing the loss of sensitive information to the investigation, thus allowing the recovery of important data to the computer forensics.
Memory forensics is a promising technique that involves the process of capturing and analyzing data stored in volatile memory. Since, by volatile memory, which means that data can be lost on system shutdown, or can be rewritten in the normal functioning of the same. This characteristic of constant flux, the data in memory are usually less structured and predictable.
DATA CONTAINED IN THE MEMORY
The overview of the information stored in memory, everything is running on a computer is stored temporarily in memory, either in volatile memory, the paging file is related to virtual memory. By extracting an image of memory known as ‘dump’ memory is possible to identify the relationship of the running processes, it is possible to establish a relationship between the processes in order to identify which processes have started other processes, likewise, is feasible to identify which files, libraries, registry keys and sockets that were in use by each process. In summary, it is possible to map how the system was being used when generating the ‘dump’ memory and also recover executable programs stored in memory.
MORE INFORMATION ABOUT “DUMPS”
This is the method currently used by the experts in computer forensics to acquire the contents of RAM.
There are several programs that help the image acquisition memory system, this work. These tools make reading memory bit-by-bit and copy its contents to a file, the “dump” of memory. This file will have the same physical memory size of the system.
What should be taken into account, regardless of the tool being used, is that, as shown by the “Locard Exchange Principle”, when an acquisition program dump is executed, it must be loaded into memory, meaning it will traces, and that some of the memory space that could contain valuable information will be used, and can even lead to changes in the area occupied by processes to paging files. Furthermore, while the tool is reading the contents of the memory, the status of the system is not frozen, which means that while some pages are being copied, and others may be changed if the process is that use is still running, for example. What will define the time spent to collect the image are factors such as processor speed, bus fees and operations in and out of the disc.
CREATING “Forensic Image” WITH FTK IMAGER
FTK Imager is a free tool provided by Access to Data acquiring forensic images. The tool allows you to create, mainly disk images…Besides creating forensic disk images, we can perform memory dumps and even perform a forensic analysis on the small image created. There are many other fucionalidades you will discover when you are working with it. The FTK Imager was created by the company AccessData and is free.
STEP TO STEP
Well, I’m looking for a simple and practical way to demonstrate these concepts. Let’s click on the “File” menu and click the “Create Disk Image” and choose which disk or partition, or we will make the image. To choose the option to perform a forensic image of the disc, we will on the “Physical Drive”, if we want to make the image of a partition, let the option “Logical Drive”. Look the pictures below:
Figure 1) FTK Imager.
Figure 2) Logical Drive.
Figure 3) Physical Drive.
Then I’ll do the forensic image of a USB stick plugged into my machine, and also choose the option “Physical Drive “. Can I choose which device I want to make the image and then I click on the “Finish” button.
Figure 4) Select Drive.
Now click on “checkbox Verify images after area They created”. With this option selected, the tool will calculate the “hash” MD5 and SHA1 image created after that, click the “ADD” button.
Figure 5) Create Image.
Let’s select “RAW”, to perform forensic image format which is the tool of “DD” and click “Next”.
Figure 6) Select RAW.
Will request some information on evidence. We can fill these information . After that, click on “Next”.
Figure 7) Evidence Item Information.
Figure 8) Select Image Destination.
We will choose the output directory (where the forensic image is saved). “Image Filename” is where you must enter the filename of my image. In the “Image Fragment Size” I can put zero because I do not want my fragmented image. If I wanted to break into pieces, I put this field size in MB that every piece of my image would have. After that , just click on the “Finish” button.
Figure 9) The output directory.
Just click on the “Start” button.
Figure 10) Create Image.
Figure 11) Image Summary.
When the process of image acquisition forensics has finished , we can display a summary with various information.In the same directory where the image was stored was created a “txt”, which is like a log , which has the same summary information.