Phishing emails are commonly used to distribute malware and in recent years malware loaders have been a common payload. Malware loaders include the likes of BazarLoader and Bumblebee, which are used to infect devices with the goal of delivering the malware and ransomware payloads of other threat groups.

Security researchers have identified a relatively new malware loader dubbed Matanbuchus that is being delivered via phishing emails. Like other malware loaders, Matanbuchus is operated under the malware-as-a-service model, and has been developed to stealthily download and execute second-stage malware payloads and executable files. The Matanbuchus loader has recently been observed dropping Cobalt Strike on infected systems. Cobalt Strike is a legitimate adversary simulation framework that is used in red team operations for detecting vulnerabilities that could potentially be exploited, but is also extensively used by criminal hackers for post-exploitation activities.

The Matanbuchus loader is currently being offered on Russian cybercrime forums for $2,500, and has been available since at least February 2021, with a malware developer operating under the moniker BelialDemon believed to be the developer of the malware. BelialDemon is known to have been involved in the development and sale of other malware loaders, such as TrumpLoader.

Matanbuchus, which is an alternate name for the demon Belial, can be used to launch an .exe or .dll file in the memory, add or modify task schedules, launch PowerShell commands, and execute standalone executable files to load a DLL. The malware has already been used in several attacks in the United States, including entities in the education sector.

Researchers at Palo Alto Networks’ Unit 42 team have identified phishing emails being used to deliver the Matanbuchus loader that use Excel documents with malicious macros. As is common in these types of phishing campaigns, if the user opens the attached file, they are informed that the document was created in an earlier version of Microsoft Excel, so the content cannot be viewed unless the user clicks on Enable Editing and then Enable Content. Should content be enabled, Excel 4.0 macros are then leveraged to drop and execute the Matanbuchus loader.

A campaign has also been detected that uses a .zip file attachment that contains an HTML file, which delivers a second .zip file that includes an MSI installer. If that file is executed, an error message is displayed indicating to the user that something has gone wrong, when in the background a DLL file is delivered and executed, which acts as the loader for delivering the Matanbuchus loader DLL file.

To block the delivery of malware loaders such as Matanbuchus, it is important to implement multiple cybersecurity solutions. A Spam filter such as SpamTitan can be used to block the delivery of the phishing emails. SpamTitan includes dual antivirus engines for detecting and blocking known malware and sandboxing to identify unknown malware through in-depth analysis of the behavior of attached files.

A web filter such as WebTitan should be used to block connections to malicious websites that host the malware. WebTitan can also be configured to block downloads of files often used to deliver malware and command-and-control center communications.

It is also strongly recommended to provide comprehensive security awareness training to all members of the workforce to explain the threat of phishing emails, explain the red flags to look for in emails, and not to open attachments unless they can be verified as authentic. TitanHQ can help in this regard through the SafeTitan Security Awareness Training solution, which includes a phishing simulation platform for simulating phishing emails to test how employees respond. For further information on these solutions, contact TitanHQ today.