Organizations worldwide have been warned of an increase in the number of attacks abusing Microsoft OneNote documents for malware delivery.
Part of the Office suite, OneNote is typically used within organizations for note taking and task management, among other operations.
What makes OneNote documents an attractive target for threat actors includes the fact that they do not benefit from the Mark-of-the-Web (MOTW) protection, along with the fact that files can be attached to OneNote notebooks and then executed with minimal warnings.
In August last year, security researchers warned that MOTW was not applied to OneNote attachments, meaning that unsigned executables or macro-enabled documents could be used to bypass existing protections.
According to WithSecure, however, Microsoft last month silently patched the ability to bypass MOTW for OneNote attachments, which decreases the potential for abuse, but does not completely eliminate it, allowing threat actors to embed files in OneNote documents and lure users into executing them.
Attacks abusing OneNote documents for malware delivery are not different from those using other types of malicious Office files: under different pretenses, the user is tricked into opening the document and enabling editing, which results in the execution of attached code.
In December 2022 and January 2023, Proofpoint observed more than 50 malicious campaigns abusing OneNote documents for the delivery of malware such as AsyncRAT, AgentTesla, DoubleBack, NetWire RAT, Redline, Quasar RAT, and XWorm.
Both Proofpoint and Sophos
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