Researchers at Trustwave warn that a phishing campaign is distributing malware via HTML attachments disguised as invoices. Notably, the HTML files abuse the Windows Search protocol to launch Windows Explorer and trick users into installing the malware.
“Trustwave SpiderLabs has detected a sophisticated malware campaign that leverages the Windows search functionality embedded in HTML code to deploy malware,” the researchers state.
“We found the threat actors utilizing a sophisticated understanding of system vulnerabilities and user behaviors....The campaign starts with a suspicious email containing an HTML attachment disguised as a routine document, like an invoice. The threat actor encloses the HTML file within a ZIP archive to enhance deception and evade email security scanners.”
When the user opens the HTML file, they’ll be prompted to allow the search function. The function will attempt to trick the user into running a malicious script.
“The attack moves to its next phase after the user permits the search action,” Trustwave explains. “The search function retrieves invoice-named files from a remote server. Only one item, particularly a shortcut (LNK) file, appears in the search results. This LNK file points to a batch script (BAT) hosted on the same server, which, upon user click, could potentially trigger additional malicious operations.”
Trustwave concludes that user awareness is necessary to thwart evolving social engineering tactics.
“The HTML document serves as a crucial component in this attack, facilitating the execution of a script that exploits the Windows search functionality,” the researchers write. “While this attack does not utilize automated installation of malware, it does require users to engage with various prompts and clicks.
However, this technique cleverly obscures the attacker’s true intent, exploiting the trust users place in familiar interfaces and common actions like opening email attachments. As users continue to navigate an increasingly complex threat landscape, ongoing education, and proactive security strategies remain paramount in safeguarding against such deceptive tactics.”
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