Security researchers discovered a new Ursnif malware delivery campaign leveraging Excel 4.0 macro functionality.

In an analysis of one Ursnif delivery campaign dating back to January, Morphisec discovered that many of the malicious files leveraged .xlsm as their extension. They also had “3” as their detection score, a rating that is too low to have static heuristic-based approaches label the files as suspicious. That caused many detection-based solutions to miss the files.

Once opened, the files leveraged text to ask that users enable editing and content. This technique helped the files to evade OCR heuristic detection methods more effectively than if the files had used an image to issue the same request.

Enabling the content activated a defining ability of Excel 4.0: the use of macro worksheets to deploy XLM macros. In this case, the heavily obfuscated sheet was hidden and leveraged several “RUN” commands before ending with some “CALL” and “EXEC” instructions. Those instructions ordered the Excel 4.0 macros to download Ursnif/Gozi via the Win32 API function.

Other Attacks Involving Ursnif

Security researchers have detected several other Ursnif campaigns over the past year. Back in August 2019, for instance, Fortinet spotted a new campaign that used Microsoft Word documents to spread a new variant of the malware.

In January 2020, the SANS Internet Storm Center picked up on a malspam campaign that preyed on German users with password-protected ZIP archives carrying the threat. Most recently in April 2020, Zscaler observed an attack campaign that embraced mshta instead of PowerShell for its second-stage payload before ultimately delivering Gozi.

Defend Against Malicious Macros

Security professionals can help defend against malicious macros by implementing logging and reviewing logs for suspicious activity that could be indicative of a malware infection. Companies should also invest in ongoing security awareness training so that employees will be less inclined to open email attachments carrying malicious macros.

More from

The Evolution of Antivirus Software to Face Modern Threats

Over the years, endpoint security has evolved from primitive antivirus software to more sophisticated next-generation platforms employing advanced technology and better endpoint detection and response.  Because of the increased threat that modern cyberattacks pose, experts are exploring more elegant ways of keeping data safe from threats.Signature-Based Antivirus SoftwareSignature-based detection is the use of footprints to identify malware. All programs, applications, software and files have a digital footprint. Buried within their code, these digital footprints or signatures are unique to the respective…

How Do Threat Hunters Keep Organizations Safe?

Neil Wyler started his job amid an ongoing cyberattack. As a threat hunter, he helped his client discover that millions of records had been stolen over four months. Even though his client used sophisticated tools, its threat-hunting technology did not detect the attack because the transactions looked normal. But with Wyler’s expertise, he was able to realize that data was leaving the environment as well as entering the system. His efforts saved the company from suffering even more damage and…

The White House on Quantum Encryption and IoT Labels

A recent White House Fact Sheet outlined the current and future U.S. cybersecurity priorities. While most of the topics covered were in line with expectations, others drew more attention. The emphasis on critical infrastructure protection is clearly a top national priority. However, the plan is to create a labeling system for IoT devices, identifying the ones with the highest cybersecurity standards. Few expected that news. The topic of quantum-resistant encryption reveals that such concerns may become a reality sooner than…

Contain Breaches and Gain Visibility With Microsegmentation

Organizations must grapple with challenges from various market forces. Digital transformation, cloud adoption, hybrid work environments and geopolitical and economic challenges all have a part to play. These forces have especially manifested in more significant security threats to expanding IT attack surfaces. Breach containment is essential, and zero trust security principles can be applied to curtail attacks across IT environments, minimizing business disruption proactively. Microsegmentation has emerged as a viable solution through its continuous visualization of workload and device communications…