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Why are Macros a Security Threat?
5/26/2023 - Brian O'Neill

typing one hand with document

What is a Macro?

Like most non-malware file upload threats, there’s nothing inherently malicious about a macro. At a high level, macros are just lines of Visual Basic (VBA) code embedded within a Microsoft document, and they’re generally intended to expedite some specific tasks performed within that document through process automation. For example, a macro might be created to automatically format text entered within specific cells in an Excel spreadsheet, or it might be used to create formulas that change based on certain evolving input criteria.

Why are Macros a Security Threat?

Despite their time-saving benefits, macros unfortunately represent a significant attack vector which threat actors exploit with relative ease. Since the introduction of macros in the early 90’s, threat actors have consistently (and quite often successfully) used them to inject malware onto client devices, often compromising systems completely while also gaining exponential access to new victims through those systems. Since macros can be primed to run based on simple document events (e.g., when a document is opened), all it takes is one errant double-click from a system user to trigger a full-blown malware crisis.

Contributing to the challenge of mitigating macro threats is the fact that Microsoft document formats are ubiquitous in professional systems. Files like .DOCX and .XLSX, for example, are used widely in professional environments all around the world, which means system users naturally expect to see them attached to emails and saved within important shared folders. By applying basic social engineering techniques, threat actors can share documents containing malicious macros (or encrypted .ZIP archives containing multiple infected documents) from compromised devices, assuring the recipient that enabling the macro provides access to necessary content. They can also share their infected document through an insecure file upload portal, waiting patiently for a downstream internal or external user to access that file and unleash its contents.

How are Macro Threats Mitigated?

Recent versions of Microsoft Office disable macros by default, so keeping systems up to date is an important first step. Additionally, regular user training is critical to prevent the spread of any type of malware through social engineering techniques; system users should always know how to identify suspicious emails and subsequently avoid clicking on their attachments.

A comprehensive anti-macro policy can also be configured within the Cloudmersive Advanced Virus Scan API request body. Setting the allowMacros Boolean to “False” will return a CleanResult: False response for any files containing macros, making it easy to delete or quarantine these files alongside other virus, malware, and non-malware content threats. This API references a continuously updated list of more than 17 million virus and malware signatures, including ransomware, spyware, trojans and more, and it delivers high-speed, sub-second typical response times.

For more information on Cloudmersive Virus Scanning APIs, please feel free to contact a member of our sales team.

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