Microsoft Warns of Late-Year Spike in Office Threats

Online attackers are using recent Office exploits and increasingly sophisticated methods to infect PCs, warns the software giant.


Office exploits are hardly new, but there has been a noticeable uptick in attacks in the fall of 2017 that target the popular business productivity software suite from Microsoft.

In a Nov. 21 advisory, Microsoft's Office 365 Threat Research team said that they had observed an escalation in the efforts of attackers to infect systems running Office. This new wave of activity can be traced to some recently-disclosed exploits, which are now serving as launching pads for complex attacks, according to the group.

"The discovery and public availability of a few Office exploits in the last six months led to these exploits gaining popularity among crimeware and targeted attackers alike," wrote Microsoft's security researchers in a blog post. "While crimeware attackers stick to payloads like ransomware and info stealers to attain financial gain or information theft, more sophisticated attackers clearly distinguish themselves by using advanced and multi-stage implants."

Microsoft singled out four vulnerabilities (CVE-2017-0199, CVE-2017-8570, CVE-2017-8759 and CVE-2017-11826), all of which have been fixed, but may still linger in organizations that have delayed or are a little behind in their security patches. The software maker noted that apart from CVE-2017-11826, a memory corruption vulnerability, attacks based on these exploits "pull the malware payload from remote locations," a technique that makes it tough for anti-virus engines and security sandboxing solutions to reliably detect malicious code, said the researchers.

Cyber-attackers aren't stopping at ransomware or attempts to pilfer valuable business data. WingBird, a form of malware that targets CVE-2017-8759, a code-injection vulnerability in Office, shares similarities with the "government-grade commercial surveillance software, FinFisher" and uses some exotic methods to evade detection, Microsoft warned.

"The interesting part of this malware is the use of spaghetti code, multiple virtual machines, and lots of anti-debug and anti-analysis techniques. Due to the complexity of the threat, it could take analysts some time to completely unravel its functionality," stated the Microsoft researchers.

Fortunately, Microsoft's business customers have a few options for dealing with these threats at their disposal.

Windows Defender Advanced Threat Protection, a cloud-based suite of security services for Office 365 and Exchange customers, uses machine learning and behavioral analytics to automatically block attacks based on the exploits and prevent emails with unsafe attachments from reaching users' inboxes. Additionally, the new Windows Defender Exploit Guard feature in Windows 10 Fall Creators Update prevents unauthorized changes to files by unknown exploits and blocks malicious documents with its Attack Surface Reduction component.

Not all Office-based attacks rely on an exploit.

Recently, attackers have been using the Dynamic Data Exchange (DDE) protocol to infect PCs with malware. DDE is used by Office documents to access external data sources. Used improperly, it can be used to embed links to dangerous code that prompts Office applications to download and run damaging malware.

Internet security firm Zscaler has detected at least three malware campaigns that use the technique. Microsoft advised Office users to exercise caution when they encounter suspicious email attachments and heed the alerts generated by Office's security-enhancing Protected Mode.


Pedro Hernandez

Pedro Hernandez

Pedro Hernandez is a contributor to eWEEK and the IT Business Edge Network, the network for technology professionals. Previously, he served as a managing editor for the network of...