Identifying a User Form in an Office Document

In this post, we will be looking into ways to identify and analyze the presence of a user form in an office document. As I discussed in a previous post, user forms are often used to store resources needed by the malware author such as scripts (PowerShell, VBS), shellcode and strings. We will be using OLEDUMP to assist in our analysis and by the end of this post, you will be able to identify and trace the usage of user forms and their objects throughout macro code. For this analysis, we will be looking at the following malicious office document….

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Analyzing Malicious Office Documents with OLEDUMP

Microsoft office documents are a common vehicle used by malware authors to deliver malware. These documents, used for malicious purposes, are commonly referred to as maldocs. While there has been a variety of ways in which they have been used, one of the more prevalent is through the use of macros. Macros are written in Visual Basic for Applications (VBA), which is well documented on the Microsoft Developer Network (MSDN). This API allows malware authors to hook into life-cycle events of a document, such as AutoOpen, AutoClose and AutoExit (MSDN) in order to achieve code execution with minimal interaction from…

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ToorCon XX

I had the opportunity to give a talk on malware obfuscation techniques this weekend at ToorCon XX, my talk was titled “Following a Trail of Confusion”. Here is the abstract: Modern malware uses a wide variety of code obfuscation techniques to hide it’s true intentions and to avoid detection. In this talk, we’ll explore the latest in native code obfuscation techniques as well as a few techniques commonly used with interpreted languages. We will spend time discussing such methods as dynamically constructing import tables, hiding and using shellcode, packing, string obfuscation, use of virtual machines and other anti-analysis techniques. We’ll…

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