Dynamic Analysis Techniques
As we have covered the malware analysis basics with static techniques here, this post is all about performing the basic analysis of malware using dynamic technique.
As we have seen in the previous post, the ability to fully perform malware analysis is very much restricted using static techniques either due to obfuscation, packing, or the analyst having exhausted the available static analysis techniques.
Before performing dynamic malware analysis, be sure to do it in a safe environment. Consider deploying a Windows virtual machine and using VMware for provisioning virtual machines. You should also take a snapshot of the virtual machine before executing the malicious binaries so that the safe state can be easily restored.
Analyzing with Process Monitor
Process Monitor is an advanced monitoring tool for Windows that provides a way to monitor certain registry, file system, network, process, and thread activities. Process Monitor monitors all system calls it can gather as soon as it is run. Since there are always huge number of calls being made in the Windows OS, it is sometimes impractical to discover important events. Process Monitor helps this issue with a filter tab through which we can filter by the type of calls. For example, see the screenshot below. It shows that I have applied a filter with operation of “WriteFile” and “RegSetValue”. These are usually the call made by a malicious executable to write the file onto the disk and to make registry changes.
After applying the filter, we get a list of following events in Process Monitor.
The most important are the top two entries which shows the execution of file and creation of registry entry with a new entry named “Video Driver.” Other entries can be ignored as it is usual for pseudorandom numbers to be generated.
On clicking the first entry, we can even see that what action that call has made. As is clear from the screenshot below, a total 7168 bytes have been written to the file system by this binary.
Analyzing with Process Explorer
Process Explorer is a tool used for performing dynamic analysis and can give you a great insight onto the processes currently running onto the system. Below is an example of the process being created after running a binary. Clicking on process can help you reveal whether the process has created any mutant or not.
Also it can give you all the information about the DLLs being used by the function. Below, the screenshot shows that the process uses ws2_32.dll, which means that a network connection will be made by this process.
Double clicking a particular process will yield more information about the process. Some of the important attributes are:
Verify Option. There is a verify option in every process to check whether that binary is signed by the MS or not. Below, the screenshot depicts that this binary is not signed by the MS.
- Threads will showcase the number of threads associated with this process.
- Strings tab can help in determining whether there is any process replacement occur or not. If two strings are drastically different then the process replacement might have occur. Below, the screenshot shows that strings in the executable both on disk and in memory.
INetSim is a free Linux based suite for simulating common Internet services. It is sometimes difficult to analyze a malware without letting it complete execute the code and that can involve contacting the outer world for services over http, https, FTP etc. INetSIM does exactly this by emulating services like Http, Https, FTP and allows analyst to analyze the behaviour of malware. Since this is Linux based, the best way to use this is to install it on a Linux machine and keep it in the same network as that of windows testing machine.
INetSIM can serve any type of request that the malware might request for. For example, suppose a malware requests for an image from the for tis code to execute. INetSIM can fulfil the request of the malware though the image will not be what malware will be looking for but it will keep the malware to keep executing the code. INetSIM can also log all the request from the client regardless of the port. This can be used to record all the data sent from malware.
In the next series, we will move to advanced techniques of malware analysis using both static and dynamic analysis.
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