Unknown threat actors have exploited a now-patched security flaw in Microsoft MSHTML to deliver a surveillance tool called MerkSpy. This campaign primarily targets users in Canada, India, Poland, and the U.S. MerkSpy clandestinely monitors user activities, captures sensitive information, and establishes persistence on compromised systems. The attack starts with a Microsoft Word document that contains a job description for a software engineer role.
Opening the document triggers the exploitation of CVE-2021-40444, a high-severity flaw in MSHTML, allowing remote code execution without user interaction. This leads to the download of an HTML file from a remote server, which initiates the execution of embedded shellcode after checking the operating system version. The shellcode serves as a downloader for a file deceptively titled “GoogleUpdate,” which hides an injector payload responsible for evading detection by security software.
MerkSpy establishes persistence on the host through Windows Registry changes, launching automatically upon system startup. It captures sensitive information such as screenshots, keystrokes, login credentials stored in Google Chrome, and data from the MetaMask browser extension, transmitting this data to an external server controlled by the threat actors. This comprehensive data exfiltration poses significant risks to the affected users.
Symantec has also detailed a separate smishing campaign targeting U.S. users with SMS messages purporting to be from Apple. These messages aim to trick users into clicking on bogus credential harvesting pages. The malicious website mimics an outdated iCloud login template, adding a CAPTCHA for perceived legitimacy. This highlights the growing sophistication and variety of cyber threats targeting users worldwide.
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