Cuckoo Malware Analysis: Analyze malware using Cuckoo Sandbox

There are two common methodologies of the malware analysis process commonly used by malware analysts: static analysis (or code analysis) and dynamic analysis (or behavior analysis). These two techniques allow analysts to understand quickly, and in detail, the risks and intentions of a given sample malware.

For performing static analysis, you need a strong understanding in programming and x86 assembly language concept. During the static analysis process, you don't have to execute the malware. Generally, the source code of malware samples is not readily available. You have to do disassembling and decompiling first, and after successfully performing reverse engineering you can analyze the low-level assembly code. Most malware analysts perform a static analysis at an earlier stage in the malware analysis process because it is safer than dynamic analysis. The challenge in static analysis is the complexity in modern malware, where some of the malware implement anti-debugging systems to prevent malware analysts from analyzing the pieces of code.

Dynamic analysis (behavior analysis) is a process in malware analysis that performs an execution of the malware itself and observes the malware activity. It also observes the changes that occur when the malware is being executed. Infecting a system with malware from the wild can be very dangerous. Malware infection on your system can cause damage to your system such as file deletion, change in registry, file modification, stealing confidential data/information, and so on. When performing malware analysis, you need a safe environment and the network should not connect to production networks. With dynamic analysis, you can monitor the changes made to the filesystem, registry, processes, and its network communication. The advantage of performing dynamic analysis is that you can fully understand how a malware works.

To handle the number of malware samples, some automated malware analysis techniques have been developed. Automating some aspects of malware analysis is critical for organizations processing large numbers of malicious programs. Automation will allow analysts to focus more on the tasks that need more attention in human analysis.

When using Cuckoo as an automated malware analysis tool, it is expected to reduce the amount of time analyzing a malware in a conventional way. There are some steps in dynamic malware analysis that require a lot of time; one of the instances are while we're setting up a virtualized environment for a malware to run. The process may seem easy, but if we have several malware to analyze, it will be pretty time-consuming.

As malware became more sophisticated, we needed more technology that would allow us to analyze malware easily without compromising our system. One such technology that can be used is sandboxing. Sandboxing has a wide and various explanation among IT people. For a reference, you can see the explanation from Wikipedia at http://en.wikipedia.org/wiki/Sandbox_(computer_security). In specific terminology (computer security), sandboxing is a technique for isolating a program (in this case, malware) by providing confined execution environments, which can be used for running unreliable programs from the main environment. To give a clear explanation about sandboxing technology, let's imagine a sandbox or sandpit playground for children. Sandpit is a container filled with sand for children to play. The "pit" or "box" itself is simply a container for storing the sand so that it does not spread outward across lawns or other surrounding surfaces. The children can do anything in the sandpits as long as they are still in the sandbox. By providing a sandbox, we can execute malicious applications and see the malware activities.

We can also analyze the malware safely and securely without worrying about the changes that will occur during the process. There are several malware sandboxes you can use for building your own automated malware analysis lab. For example, Buster Sandbox Analyzer, Zero Wine, Malheur, Cuckoo Sandbox, and so on. Cuckoo is the right tool to perform an analysis for a sandboxed malware because Cuckoo has a complete feature, it is fully open source, and has good support from its community.

What is a malware analysis lab, and why should we build a malware lab? Malware lab is a safe environment to analyze malware. Basically, it is an isolated environment which contains a lot of useful tools for malware analysts that helps them in analyzing the malicious software. We should build a malware lab to be more proactive to new and modern threats that can suddenly attack our organization. It is also a form of advanced detection before antivirus vendors found a new malware specimen. The scope of the malware analysis lab can be determined by examining the processes that will occur in the malware analysis process.

Static analysis involves disassembling and reverse engineering the code of the malware. This can be done in a static state where the code is analyzed without being executed. No complex configuration is required for the lab, because actually you won't execute the malware itself. This lab is provided just to safeguard if you accidentally execute the binary malware when you are performing the code analysis. For dynamic analysis, you need to set up a more complex lab, as you need to execute the malware. Malware behaves differently depending on the operating system environment where they are being executed.

You should pay more attention regarding the location of malware analysis hosts on your network. Trojan, worms, and other types of malware can be self-replicating, so it's highly likely that simply running an executable code on a production network can lead to another machine on the same network being infected.

Setting up a malware analysis lab is actually quite simple and requires a minimum amount of hardware. Isolating your malware analysis lab from other computers in the network is not enough. In addition, you also need to isolate your lab from the Internet if you are not sure. You should consider this option, because sometimes a malware needs to communicate with the malware author server, for example, Botnet command and control servers.

There are two options in building a malware analysis lab, that is, a physical environment and a virtualization environment. As mentioned earlier, both of them have advantages and disadvantages. Building your physical lab will require a lot of money and time in building the environment as well. In this situation, building a malware lab using the virtualization technique will save your money and time. Virtualization software allows you to save the state of a virtual machine as it runs so that you can revert back to it when necessary. This term is usually called snapshot. Using this snapshots feature, you can have a virtual machine environment that contains an operating system with a full set of weapons of dynamic and static analysis tools, and then perform a dynamic analysis with the malware, and finally you can save the session using the snapshot feature so that you can load the initial infected state at will. After finishing your malware analysis, you can choose to save or discard that snapshot and revert back to a clean image. Then, using the snapshot feature, you do not have to worry about malware that will infect your Guest OS, as you will be able to easily restore to the previous state.

From now on, you can be aware that the automated analyses of malware, which uses virtualization in operating systems, will help you to shorten the time in analyzing malware samples. Virtualization technologies have become a key component in automated malware analyses because of the cost effectiveness in hardware consumption and CPU resource utilization. By using a popular operating system and intentionally infecting it with a captured malware sample, it is generally useful to monitor the activities of the malware and determine the suspicious activities that occurs. The drawback of implementing automated malware analysis is that this method can be easily detected by malware writers as it frequently uses evasion techniques such as anti-debugging, packers, encryption, obfuscating code, and so on. But you can try to hide as many virtualization traces as possible. There is a lot of information on the Internet regarding virtualization detection techniques and countermeasures of malware analysis.

As described in its official website (http://www.cuckoosandbox.org/), Cuckoo is a malware sandboxing utility which has practical applications of the dynamical analysis approach. Instead of statically analyzing the binary file, it gets executed and monitored in real time. As a simple explanation, Cuckoo is an open source automated malware analysis system that allows you to perform analysis on sandboxed malware. Cuckoo Sandbox started as a Google Summer of Code project in 2010 within the Honeynet Project. After the initial work during the summer of 2010, the first beta release was published on February 5th, 2011, when Cuckoo was publicly announced and distributed for the first time.

Cuckoo was originally designed and developed by Claudio "nex" Guarnieri, who is still the main developer and coordinates all efforts from joined developers and contributors. In March 2012, Cuckoo Sandbox won the first round of the Magnificent7 program organized by Rapid7. Cuckoo was chosen by Rapid7 for the first round of Magnificent7 sponsorships due to the developers' innovative approach to traditional and mobile-based malware analysis. Cuckoo is used to automatically run and analyze files and collect comprehensive analysis results that outline what the malware does while running inside an isolated Windows operating system. Cuckoo is designed for use in analyzing the following kinds of files:

Cuckoo can also produce the following types of results:

Cuckoo Sandbox consists of a central management software, which handles malware sample executions and analyses.

Each analysis is launched in a fresh and isolated virtual machine. Cuckoo's infrastructure is composed by a host machine (the management software) and a number of guest machines (virtual machines for analysis).

The host runs the core component of the sandbox that manages the whole analysis process, whereas the guests are the isolated environments where the malware actually get safely executed and analyzed. The following diagram shows Cuckoo's architecture:

Let us see what the important components are when installing Sandbox.

$ sudo apt-get install python

$ sudo apt-get install python-sqlalchemy

$ sudo pip install sqlalchemy

$ sudo apt-get install python-dpkt python-jinja2 python-magic python-pymongo python-libvirt python-bottle python-pefile ssdeep

$ sudo pip install dpkt jinja2 pymongo bottle pefile

$ cd /opt
$ git clone https://github.com/kbandla/pydeep.git pydeep
$ cd /opt/pydeep/
python setup.py build
sudo python setup.py install

$ sudo apt-get install automake -y
$ cd /opt
$ svn checkout http://yara-project.googlecode.com/svn/trunk/yara
$ cd /opt/yara
$ sudo ln -s /usr/bin/aclocal-1.11 /usr/bin/aclocal-1.12
$ ./configure
$ make
$ sudo make install
$ cd yara-python
$ python setup.py build
$ sudo python setup.py install

$ sudo apt-get install tcpdump

$ sudo setcap cap_net_raw,cap_net_admin=eip /usr/sbin/tcpdump

$ getcap /usr/sbin/tcpdump /usr/sbin/tcpdump = cap_net_admin,cap_net_raw+eip

$ sudo apt-get install libcap2-bin

$ sudo chmod +s /usr/sbin/tcpdump

$ uname –a

Linux digit-labs 3.5.0.17-generic #28-ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64x86_64 x86_64 x86_64 GNU/Linux

$ apt-get install linux-headers-3.5.0.17-generic

$ sudo /etc/init.d/vboxdrv setup
* Stopping VirtualBox kernel modules         [OK]
* Recompiling VirtualBox kernel modules        [OK]
* Starting VirtualBox kernel modules        [OK]

Preparing the Guest OS

The required specifications to set up the Guest OS are listed as follows:

• 1GB RAM memory

• 10 GB of hard disk space

• VDI format for the virtual disk

• Dynamically allocated storage

• Windows XP SP3

Note

When you are installing the Guest OS, you have to create the Guest OS name for the Cuckoo Sandbox VirtualBox configuration file.

In the first step, we will create the guest OS. You can write down your guest OS name, and operating system type. Since we are using Windows XP as guest OS, you can choose Windows XP in the OS type and version.

Before you start your Guest OS in VirtualBox, you need to configure the network, sharing folder, and the installing of VirtualBox Guest Addition to improve its capabilities in the malware analysis process.

Configuring the network

Basically, VirtualBox has several types of network configuration that can be used by the Guest OS. Each type has a different capability based on your need, we can learn more about it in the VirtualBox website:

http://www.virtualbox.org/manual/ch06.html

Tip

Cuckoo is written in Python language, so you will need to install Python and other libraries as dependencies. Here is a website for you to download malware samples from, which will be used in this book:

http://www.cuckoosandboxbook.com/

You can download malware samples from the website. They will also provide you with some useful tools that can be downloaded from the same website. If you want to get additional information about this book, you can visit the aforementioned website, and put your comments there.

Based on the explanation in the website, we should use the Host-only networking type, because it will isolate our Guest OS from the outside network. With this networking type, Host OS and Guest OS can interact with each other, but the Guest OS can "see" the outside network or internet.

1. In the VirtualBox main window, click on the File button and select Preferences...:

   

2. Choose Network in the sidebar to configure your host-only networking, and then click on the green icon that says Add host-only network (Ins) if you hover over it:

   

3. Click on the last icon on the side pane that says Edit Host-only Network to view your network configuration. If the DHCP server is not enabled, you need to manually configure your Guest OS IP Address but I suggest you leave it as it is:

   

4. Next, you need to set up your Guest OS. Choose your Guest OS first in the sidebar, then click on the Settings option in the VirtualBox main window, and choose Network:

   

5. Go to the Adapter 1 tab and tick the option Enable Network Adapter. In the Attached to drop-down menu, you have to choose Host-only Adapter and in the Name drop-down menu choose vboxnet0 (network adapter name is based on what you have created).

6. After finishing your configuration for the Guest OS, you can start your Guest OS into the beginning installation process.

I assume that you have already finished your Guest OS installation process and logged in to your Guest OS. You will need to manually configure your Guest OS, as the DHCP server is not enabled in the host-only network configuration. Give your OS IP address with the same network segment as the Host OS. In this case, if you leave the host-only configuration as it is, the Host OS and Guest OS IP addresses will be set as 192.168.56.1 and 192.168.56.101, respectively.

Try to ping each other to make sure that the Host OS and Guest OS is already connected.

Setting up a shared folder between Host OS and Guest OS

1. In the Guest OS main window, click on the Devices option and select Shared Folders... as shown in the following screenshot:

   

2. Then click on the green icon at the top-right corner of your window that says Add Shared Folder (Ins):

   

3. Choose the folder (in your Host OS) that you want to be shared with your Guest OS in the Folder Path (for example /home/username/Downloads or we can make our own folder somewhere else).

4. Give the shared folder a name (by default your computer will give a shared folder name, you can change the folder name as you wish), and tick the sharing options according to your choice:

   

5. Now in your Windows Guest OS, click on the Start menu, right-click on My Computer, and choose Map network drive....

6. Select the drive you want from the drop-down menu.

7. In the Folder text field, fill it in with \\vboxsrv\shares (shares is the shared folder name in the previous screenshot).

8. Go to Computer or Windows Explorer, and you will see the shared folder.

9. Now, to configure your Guest OS you have to:

   1. Install Python for Windows. You can download the software at http://python.org/download/.

   2. Install PIL (Python Imaging Library) Python module to created desktop screenshots. This software is available at http://www.pythonware.com/products/pil/.

   3. Turn off automatic Windows updates.

   4. Turn off Windows firewall.

   5. Install third-party applications (Microsoft Office 2003/2007, Acrobat Reader 9.5, Mozilla Firefox 3.6, and so on) at http://www.oldapps.com/. This step is optional.

10. Next, copy the Python agent to our Windows shared folder using this command line on the Host OS:

    $ cp /home/digit/cuckoo/agent/agent.py /home/digit/cuckoo/shares/
    

11. From your Windows Guest OS, copy the agent.py file into C:\Python27 folder.

12. Rename the agent.py file to agent.pyw.

    PYW files run the script without invoking the console window, especially if your program is GUI based. If you double-click the agent.py file, a command prompt window will appear on your desktop. If you rename the file to a .pyw file, there will be no pop-up window appearing on your desktop. It is similar to a background process in Linux.

13. To always run the agent.pyw file in startup process, you need to put it in the Startup folder in the following paths:

    For Windows XP go to C:\Document and settings\username\Start Menu\Programs\Startup.

    For Windows 7 go to C:\Users\iKONspirasi\AppData\Roaming\Microsoft\WIndows\Start Menu\Programs\Startup.

14. After executing agent.pyw, a new socket will be listening on the 0.0.0.0:8000 port. To check it, you should run this command in the command prompt:

    C:\>netstat –aon
    

    As you can see in the screenshot below:

    

15. You also need to configure Host OS IP forwarding and filtering rules using Iptables:

    $ iptables -A FORWARD -o eth0 -i vboxnet0 -s 192.168.56.0/24 -m conntrack --ctstate NEW -j ACCEPT 
    $ iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT 
    $ iptables -A POSTROUTING -t nat -j MASQUERADE 
    $ sysctl -w net.ipv4.ip_forward=1 
    

16. The next step is the configuration of Cuckoo Sandbox.

$ sudo adduser cuckoo

$ sudo usermod -G vboxusers cuckoo

$ sudo usermod -G libvirtd cuckoo

# Add your VirusTotal API key here. The default API key, kindly# provided by the VirusTotal team, should enable you with a # sufficient throughput and while being shared with all our users, # it should not affect your use.

key = a0283a2c3d55728300d064874239b5346fb991317e8449fe43c902879d758088

$ vboxmanage snapshot "WIndows-cuckoo" take "WIndows-cuckooSnap01" --pause 

$ vboxmanagecontrolvm "WIndows-cuckoo " poweroff
$ vboxmanage snapshot "WIndows-cuckoo" restorecurrent
$ vboxheadless --startvm "WIndows-cuckoo"

Now, you have successfully prepared the Host OS and Guest OS in the VirtualBox and then installed Cuckoo Sandbox. It is important to make sure that all the dependencies that are needed in the Host OS along with pydeep and yara are present. For the Guest OS, always turn off the defensive parameter and Windows firewall and use any software that the malware often use to interact with, for example, Adobe Reader 9.5, Internet Explorer 6, Microsoft Office 2003, and so on.

Always set your configuration in <machinemanager>.conf in exactly the same way as it is in the virtualization software you are using. For example, if you are using KVM, you have to set kvm in machinemanager.conf. Since we are using VirtualBox, you have to set virtualbox in the configuration. You have to be careful at the time of inserting the name of the Guest OS in VirtualBox to cuckoo.conf configuration file. For example, if you create a Guest OS named cuckoo1, you have to write down cuckoo1 in the cuckoo.conf configuration file. The most important part of all is not to forget to make a backup of the whole system and configurations.

In the next chapter, we will continue learning about Cuckoo Sandbox's features, such as analyzing PDF files, URLs, and binary files, Memory Forensic using Cuckoo Sandbox (using the Memory dump feature), and additional Memory Forensic using Volatility.