Malware Analysis How to Analyze Malicious Microsoft Office Files

Andy Ful

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Phishing attacks are one of the most common causes of security breaches according to Verizon’s 2021 Data Breach Investigations Report. Most phishing attacks arrive via emails containing malicious attachments. A seemingly innocent Microsoft Word file, for example, can be the initial infection stage of a dangerous attack where a threat actor uses a document to deliver malware.​

Handling Malicious Microsoft Office Files During Incident Response​

When handling a security breach, the incident response team will collect suspicious files and evidence from the compromised endpoint in order to investigate the incident. One of the challenges IR teams face is finding all of the malicious files that were used in the attack and classifying them to their relevant malware family.

Binary files are usually the main suspect. We know that malicious code was executed, so we search for suspicious binary files containing this code (looking for recently installed programs, for example). Non-binary files like Microsoft Office documents should also be carefully examined because they can be the first stage of an attack that caused the malware execution to begin with.

Office documents are widely used by threat actors to deliver malware. Usually, the file is attached to an email that is crafted to look like a legitimate communication. Threat actors use social engineering techniques to persuade the victim into opening the malicious attachment.

In this article, we will explain the different types of Microsoft Office file formats and how attackers abuse these documents to deliver malware. You will also be presented with tools and techniques that can help you better identify and classify malicious Microsoft Office files.​

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SecureKongo

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