Tag Archives: ProcDOT

Dynamic Malware Analysis with REMnux v5 – Part 2

procdotDuring part one we created the environment to perform dynamic malware analysis with REMnux toolkit. Then the malware was executed and  all the interactions with the network were observed and captured. Essentially,  the malware was executed in a disposable virtual machine and all the traffic – including SSL – was intercepted.

Now, to further acquire information that would help us answering the questions made during part 1, it would be relevant to observe what happens at the system level.

Below recipe involves running Process Monitor from Sysinternals. Process Monitor is an advanced monitoring tool for Windows that shows real-time file system, Registry and process/thread activity, In parallel we run a packet capture with Wireshark on the disposable machine or we run tcpdump on REMnux. These tools will be started before malware executed and stopped moments after the infection. Then we will import this data – pcap and procmon – into ProcDOT. ProcDOT is a free tool created by Christian Wojne from CERT.at. It runs on Windows or Linux and is installed on REMNux This tool has the capability to parse the Procmon data. Then correlates it with the pcap  and transforms the data into a picture. This enables malware visual analysis. This method can be of great help for a effective and efficient dynamic malware analysis. The steps using part 1 model are:

 

  • Restore the VMware snapshot.
  • Start Process Monitor (need to be installed beforehand) and configure Columns fields to be compatible with ProcDOT.
  • Start Wireshark or tcpdump on REMnux and start capturing traffic.
  • Copy the malware to the virtual machine and run the malware.
  • Stop the wireshark capture and export the traffic into PCAP.
  • Stop the Process Monitor capture and export the results into CSV.
  • Move the PCAP and CSV file to REMnux.
  • Power off the infected machine.
  • Execute ProcDOT and import the procmon and pcap data.
  • Select the process and render the analysis.
  • Run trough the animation to understand the timing aspects.

The picture below demonstrate the result (for the sake of size elements such of registry key and paths have been removed):

procdot-torrentlocker

 

This visualization technique is very helpful in order to determine in a very quick way what the malware does. The graph produced by ProcDOT is interactive and you can play an animation of it in order to determine in which sequence the events occurred. In this case several relevant events happened. You can easily observe that:

  • The executable torrentlocker.exe starts execution and invokes a new thread id 1924
  • The thread id 1924 creates a new suspicious file named 01000000
  • Thread id 1924 creates a new process named “explorer.exe” with pid 1928
  • This new process creates several actions including
  • A suspicious executable file is created under c:\windows named izigajev.exe
  • A new AutoStart registry key is created invoking the just created executable file
  • The file Administrator.wab is read and data written to it.
  • A new process name vssadmin.exe is invoked

By looking at this sequence of events we can conclude that the malware performs process injection by injecting its malicious code into a benign process. Creates a copy of itself and drops it into Windows folder. Maintains persistence by adding the dropped executable into the auto start registry key and creates several suspicious files.

A very simple, fast and effective method that can speed up the malware analysis. Using this visual analytic technique and the one described on part one you can gather indicators that could now be used to identify the malware in motion (network) or at rest (file system/registry) across your network. Further they could be used to augment existing security controls and find additional infected systems.

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Malicious Documents – Word with VBA and Powershell

E-mail continues to be the weapon of choice for mass delivering malware. The tools and techniques used by attackers  continue to evolve and bypass all the security controls in place. These security controls  could be a simple home based UTM device or a big corporation security infrastructure with all kinds of technology. Social engineering methods, combined with latest encoding and obfuscation techniques allow e-mails to be delivered straight to the end user mailbox. These phishing e-mails attempt to steal confidential data such as credentials using all kinds of deception techniques to lure users to click on links or open documents or give their information. In the last days I came across some of these documents. The below steps describe the mechanism behind one of these documents (MD5: 4a132e0c7a110968d3aeac60c744b05a)  that when opened on Microsoft Office lure the victim to enable macros to view its content. Even with macros disable many users allow the macro to execute. What happens next?

  1. The malicious document contains a VBA macro.
  2. The macro is password protected. The protection can be bypassed using a hex editor and replacing the password hash with a known password hash to see its contents.
  3. When executed the VBA macro writes 3 files on disk. A batch file”ntusersss.bat”, a VBS script “ntuserskk.vbs” and a powershell script “ntusersc.ps1”.
  4. It invokes cmd shell and executes the batch file which calls the VBS script
  5. Microsoft Script Host (cscript.exe) is invoked and the VBS script is executed which calls the powershell script
  6. Power shell script is executed and it downloads the malicious EXE
  7. The malicious file is stored on disk and renamed to crsss2.exe
  8. The trojan is executed and the machine is infected.

The following picture illustrates the previous steps.

feodo-docmechanics

The downloaded malware is very sophisticated and is known to be a variant of the Feodo ebanking trojan (aka Cridex or Bugat). This trojan contains advanced capabilities but the main feature is to steal credentials by performing men in the browser attacks. These credentials are then used to commit ebanking fraud . After execution, the malware contacts the Command and Control server and the machine becomes part of a botnet and starts capturing and stealing confidential data.

Another new document used recently in several phishing campaigns it also uses a VBA macro inside the word document (MD5: f0626f276e0da283a15f414eea413fee). But this time the VBA code is obfuscated. Using the Microsoft macro debugger its possible to execute in a step-by-step fashion and determine what it does. Essentially it downloads a malicious executable file from a compromised website and then it executes it.

feodo-vba

Again, after execution it contacts its Command and Control via HTTP. The computer will be part of a Botnet and it will start to steal credentials and other confidential data.

Below a visual analysis of the malware behavior starting with the Winword execution. This graph was made using ProcDOT which correlates Sysinternals Procmon logfiles with packet captures to create an interactively graph. A great tool created by Christian Wojne from the Austrian CERT. This can be of great help for a faster malware behavior analysis. It is also unbelievable to visualize how complex is malware these days. I will leave a how-to on how to produce these graphs for other blog post.

ProcDot
From a defense perspective, the US-CERT put together excellent tips for detecting and preventing this type of malware and to avoid scams and phishing attempts applicable to home users and corporations. Note that these documents were not detected by the AV engines at the time the phishing campaign was seen. Virustotal was reporting less than 5% detection rate. Even running on a limited privileges user account the attack would still be successful. A key recommendation is to use Enhanced Mitigation Experience Toolkit 5.0 from Microsoft as part of your layered defense.

feodo-emetThis is a free product from Microsoft for the endpoint and will prevent the execution of the attacks described previously and many others. Exploit mitigation technologies do not guarantee that vulnerabilities cannot be exploited. However, they raise the bar and increase the costs for the attacker to make exploitation successful by making it harder to be executed. On a windows 7 SP1 with EMET 5, when opening the documents and running the malicious VBA macros, EMET would prevent its execution.

Email attachments can be dangerous. Use caution with Email attachments!

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