Microsoft OneNote Attachments Become the Latest Method to Spread Malware

With Microsoft disabling macros by default on Office documents, cybercriminals are left needing another means to launch malware that’s victim-supported by default.
We should expect nothing less of threat actors; when pushed up against a wall with their most powerful asset – Office macros – taken away from them, the most cunning of them will find alternative method. The challenge for the most sophisticated of cybercriminals is to ensure that the greatest number of potential victims have the application needed that acts as the launcher.
According to a recent tweet from email security company Prevention Point, a new method involving weaponized OneNote attachments has been spotted in the wild.
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➡️ Malspam mail being delivered with attached onenote document
➡️ Onenote attachment contains a button that once clicked, it executes exported file located in: “C:\Users\user\AppData\Local\Temp\OneNote\16.0\Exported\{UUID}\NT\0” [1/3] pic.twitter.com/s6S7m18Fqo— Perception Point Attack Trends (@AttackTrends) January 10, 2023
Source: Prevention Point
The initial phish looks relatively standard for a socially-engineered email:

Source: Prevention Point
With the One Note execution looking somewhere between unexpected (after all, who ever needs to double-click a button within an application to see a supported document?) and sort of brilliant (I would assume that most knowledge workers haven’t interacted frequently with OneNote, so, “maybe this is how it works?”).

Source: Prevention Point
And to boot, the default installation of Office 365 (that is, the software installed on a Windows endpoint) includes OneNote.
The takeaway here is this is downright dangerous – threat actors have found yet another new way to engage with users in a way that helps move their attack forward with a double-click. This example of the constant evolution of the phish perfectly justifies why organizations need to keep users continually enrolled in Security Awareness Training so that Joe User is always kept up to date on tactics like this.
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