Connect with us

Hi, what are you looking for?

SecurityWeekSecurityWeek

Malware & Threats

Office’s OLE Leveraged to Hide Malicious Code

Malware authors are switching from macros to object linking and embedding (OLE) to hide malicious Visual Basic (VB) and JavaScript (JS) scripts in Office documents, Microsoft warns.

Malware authors are switching from macros to object linking and embedding (OLE) to hide malicious Visual Basic (VB) and JavaScript (JS) scripts in Office documents, Microsoft warns.

Just as with malicious macros before, attackers are using various social engineering techniques to trick users into enabling the hidden scripts, which in turn download malware onto the compromised machines. According to Microsoft, the use of OLE might indicate a shift in behavior as administrators and enterprises are adopting better security and new options in Office to prevent this infection vector.

In a blog post, Alden Pornasdoro, Microsoft Malware Protection Center, explains that the OLE-embedded objects and content spotted in recent cases are surrounded by well-formatted text and images, which are meant to trick users into enabling the malicious code. Pornasdoro also notes that the observed files were using malicious Visual Basic (VB) and JavaScript (JS) scripts.

The text encourages users to interact with the script embedded in the document, which results in a warning window to popup, prompting users whether to proceed or not. However, should the user choose to proceed, the malicious script runs and any form of infection can occur. What’s important to note, however, is the fact that user interaction is still required for the malicious payload to be executed, and that nothing happens if the object isn’t enabled.

Some of the malicious documents that employed this technique were seen containing language similar to that used in CAPTCHA and other human-verification tools. Moreover, Pornasdoro notes that malware authors can easily replace the OLE or embedded object in the file, thus switching between VB and JS scripts in no time. What’s more, attackers can embed any image they desire in their malicious documents, because it has nothing to do with the scripting language being used.

TrojanDownloader:VBS/Vibrio and TrojanDownloader:VBS/Donvibs were observed as the malicious payloads in the investigated documents, and Microsoft’s researcher explains that a decryption function set this campaign apart from the typical download-and-execute routine observed in this sort of infection.

Microsoft noticed that the malicious VB script would download an encrypted binary, which allows it to bypass network-based protection usually designed to recognize malicious formats and block them. After the encrypted file is saved to %appdata% with a random file name, the script would decrypt it. The decrypted binary in the analyzed sample turned out to be the Cerber ransomware, Pornasdoro says.

Apparently, the use of malicious Office documents that leverage the OLE capability to hide malware has decreased steadily since discovered in late May. Moreover, Pornasdoro notes that the two threats associated with these infection campaigns, namely TrojanDownloader:VBS/Vibrio and TrojanDownloader:VBS/Donvibs, are not particularly prevalent. However, they show large concentration in the United States.

Advertisement. Scroll to continue reading.

Given that the embedded objects and content require user interaction to execute the hidden malicious code, Microsoft recommends user education as an important aspect of mitigation. “As with spam emails, suspicious websites, and unverified apps. Don’t click the link, enable the content, or run the program unless you absolutely trust it and can verify its source,” Pornasdoro says.

One of the biggest security threats a decade ago, macro malware was rather dormant until recently, but it has returned stronger than ever, as IBM revealed in December last year. In March this year, Dridex and Locky, which abused macros for distribution, were observed using forms to hide their malicious code. In May, Microsoft researchers noticed that other macro malware families were employing new techniques to hide code and hinder detection efforts.

Written By

Click to comment

Trending

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

Join the session as we discuss the challenges and best practices for cybersecurity leaders managing cloud identities.

Register

SecurityWeek’s Ransomware Resilience and Recovery Summit helps businesses to plan, prepare, and recover from a ransomware incident.

Register

Expert Insights

Related Content

Cybercrime

The changing nature of what we still generally call ransomware will continue through 2023, driven by three primary conditions.

Cybercrime

A recently disclosed vBulletin vulnerability, which had a zero-day status for roughly two days last week, was exploited in a hacker attack targeting the...

Malware & Threats

The NSA and FBI warn that a Chinese state-sponsored APT called BlackTech is hacking into network edge devices and using firmware implants to silently...

Application Security

Virtualization technology giant VMware on Tuesday shipped urgent updates to fix a trio of security problems in multiple software products, including a virtual machine...

Cyberwarfare

An engineer recruited by intelligence services reportedly used a water pump to deliver Stuxnet, which reportedly cost $1-2 billion to develop.

Malware & Threats

Unpatched and unprotected VMware ESXi servers worldwide have been targeted in a ransomware attack exploiting a vulnerability patched in 2021.

Malware & Threats

Apple’s cat-and-mouse struggles with zero-day exploits on its flagship iOS platform is showing no signs of slowing down.

Cybercrime

No one combatting cybercrime knows everything, but everyone in the battle has some intelligence to contribute to the larger knowledge base.