When developing tools related to MS Office files such as olefile and oletools, it is often necessary to test them on many different samples of various types and sizes. It is quite easy to find malicious samples using malwr.com, hybrid-analysis.com and VirusTotal, just to name a few (see my previous post about that topic). However, finding and downloading a large number of legitimate files is a different challenge. Here are some tips to do it:
Presentation at the Toulouse Hacking Convention 2017 about Malicious VBA Macros: what they can do, how to analyze them, and how we can detect and block them before they hit end-users.
This article presents several tools that can be used to extract VBA Macros source code from MS Office Documents, for malware analysis and forensics. It also provides an overview of how VBA Macros are stored.
Many malware analysts like to use the VB Editor in MS Word or Excel to analyze malicious macros, because it provides a nice debugging environment. It is a convenient solution to run VBA code in its native context, in order to unmask heavily obfuscated macros.
ViperMonkey is an experimental toolkit that I have been developing since early 2015, to parse VBA macros and emulate their execution. This articles shows how it can be used to analyze obfuscated macros and extract hidden strings/IOCs.
This custom Google search engine helps you find malware samples containing specific strings, filenames, hashes or other IOCs. It uses the data indexed by several websites including malwr.com, hybrid-analysis.com, virustotal.com and virusshare.com.
For example, search "VB_Nam" to find malicious VBA macros, or "\objdata" to find RTF files with OLE Package objects.
mraptor is a simple tool designed to detect malicious VBA macros in MS Office files, based on characteristics of the VBA code. This article explains how it works, and how it can be used in practice.
A few days ago, @Bry_Campbell told me about a strange sample with a malicious macro, that could not be fully analyzed with online sandboxes and the usual tools.
Since 2014, malicious macros are coming back. And their success in recent campaigns demonstrates that it is still an effective way to deliver malware, sixteen years after Melissa.
This is a presentation that I gave to the SSTIC symposium in June 2015, translated to English. It explains what malicious macros can do, how their code can be obfuscated, and some of the anti-analysis tricks observed in recent cases. Then it shows several tools that can be used to analyze macros, including oledump and olevba.
It is sometimes useful to look for malware samples containing a specific string. For example, you might look for samples sharing similar code to analyze a malware campaign with different targets. Another use case is discovering the original version of a modified file, as described in my article "Unmasking Malfunctioning Malicious Documents".