Phishing Attacks Exploit Microsoft Visio Files and SharePoint

Threat actors are exploiting Microsoft Visio files and SharePoint to launch two-step phishing attacks, according to researchers at Perception Point.

“Perception Point’s security researchers have observed a dramatic increase in two-step phishing attacks leveraging .vsdx files – a file extension rarely used in phishing campaigns until now,” the researchers explain.

“These attacks represent a sophistication of two-step phishing tactics, targeting hundreds of organizations worldwide with a new layer of deception designed to evade detection and exploit user trust.”

The attacks begin with phishing emails that appear to be important business requests, such as purchase orders or proposals. The emails are sent from legitimate, compromised accounts, so they’re more likely to bypass security filters. The emails have Outlook attachments that lead to a Microsoft SharePoint page hosting a Visio (.vsdx) file.

“Inside the Visio file, attackers embed another URL behind a clickable Call-To-Action, in most cases we’ve observed it was a ‘View Document’ button,” the researchers write. “These files vary in appearance, with some even incorporating the breached user organization’s logos and branding to enhance credibility.

To access the embedded URL, victims are instructed to hold down the Ctrl key and click – a subtle yet highly effective action designed to evade email security scanners and automated detection tools. Asking for the Ctrl key press input relies on a simple interaction that a human user can perform, effectively bypassing automated systems that are not designed to replicate such behaviors.”

After clicking the link, the victim will be sent to a spoofed Microsoft 365 login page designed to steal their credentials.

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Perception Point has the story.