Category: malware

Removing Passwords from VBA Projects

malware

Occasionally I’ll encounter a maldoc that has a password-protected VBA project. While tools such as oledump may still extract the macros, the password protection is typically encountered when accessing the project through the Office/VBA IDE (which I typically use for dynamic analysis). This happens rare enough that I often forget the steps of removing the password so thought I’d start collecting possible solutions. Word – 2007+ Sample MD5: dc989fa836fa93fe1f158fa490382686Any.Run: https://app.any.run/tasks/dd8ae979-4afc-44ac-99d2-3b57f9d6e2b1Hybrid-Analysis: https://www.hybrid-analysis.com/sample/4bb275b253db05bfa23a677d3db8f78cef0d633bbef19d05e37780f61577153c?environmentId=100 With this type of document, you can rename the original file with a .zip extension, this will allow you to explore the contents. This type of file uses the…

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Maldoc drops DLL and executes via ExecuteExcel4Macro

malware

Behavioral information is a key indicator used to determine if an office document is malicious or not. I’ve recently seen a series of malicious office documents that lacked any observable process behavior – such as the execution of Powershell or JavaScript via cscript/wscript. As I began looking into this document, it became apparent why – it was using ExecuteExcel4Macro to load and execute a hidden DLL. Looking at the Macros Using Oledump, several macro streams where identified in this document (17 – 20, 23 – 24). Additionally, it contains a stream OLE 1.0 embedded data (see stream 4 above). This…

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Maldoc uses Windows API to perform process hollowing

malware, reversing

A favorite technique by malware authors is to use macros in their office documents to utilize a normal system executable and replace the code inside, a technique known as “process hollowing”. The primary goal of this post is to identify this technique and understand how it is employed. I’ve also posted a video that walks through shellcode analysis using Ghidra on YouTube Starting with the Macros To get started, inspect the macros and see where the code begins execution. For this document, this begins with the Document_Open function – which can be found in the ThisDocument stream. As is often…

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Anti-Analysis in JavaScript Executed by Windows Script Host (WSH)

malware, reversing

It’s common to see malicious office documents drop a JavaScript (JS) file to be executed by the Windows Script Host (WSH). The JS can then be used to create the necessary objects to create HTTP requests to retrieve and execute the next stage payload. For example, here is a document that drops the JS and executes it via CMD -> WSCRIPT (you can also see the use of CSCRIPT): What caught my eye with this sample was that there was no associated network traffic. While that doesn’t guarantee that the document didn’t achieve it’s objectives, I felt it was worth…

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