Hackers are exploiting a previously undisclosed vulnerability in Microsoft Word, which security researchers say can be used to quietly install different kinds of malware — even on fully patched computers, according to tech news and analysis site ZDNet.
Unlike most document-related vulnerabilities, this zero-day bug that has yet to be patched does not rely on macros — in which Office typically warns users of risks when opening macro-enabled files.
Instead, the vulnerability is triggered when a victim opens a trick Word document, which downloads a malicious HTML application from a server, disguised to look like a Rich Text document file as a decoy. The HTML application meanwhile downloads and runs a malicious script that can be used to surreptitiously install malware.
The way the virus works is simple as it targets a vulnerability in Microsoft’s Office suite, infecting Word documents, and then downloading malicious HTML applications that are disguised as makeshift Rich Text files.s
The malware then connects the HTML application to a server located elsewhere where hackers run a custom script to install malware and leave your information vulnerable.
“The vulnerability is bypassing most mitigations; however, as noted above, FireEye email and network products detect the malicious documents. Microsoft Office users are recommended to apply the patch as soon as it is available,” FireEye writes regarding what to do to combat the malware.
Researchers at McAfee, who first reported the discovery Friday, said because the HTML application is executable, the attacker can run code on the affected computer while evading memory-based mitigations designed to prevent these kinds of attacks.
Both McAfee and cybersecurity company FireEye agreed on the cause of the vulnerability. The issue relates to the Windows Object Linking and Embedding (OLE) function, which allows an application to link and embed content to other documents, according to researchers. The Windows OLE feature is used primarily in Office and Windows’ built-in document viewer WordPad, but has been the cause of numerous vulnerabilities over the past few years, ZDNet said.
The bug can be exploited on all versions of Office, including the latest Office 2016 running on Windows 10. Attacks have been spotted in the wild since January, ZDNet said.
A Microsoft spokesperson confirmed that the company will issue a fix for the bug Tuesday as part of its monthly release of security fixes and patches.