Spammers are targeting financial institutions using Excel Web Query (IQY) files that conceal a new downloader malware.

On Aug. 10, researchers at Proofpoint observed four large spam email campaigns. One of the campaigns carried undisguised IQY attachments with names such as “sales” and “major bank” to prey upon financial organizations. Two of the other operations passed around IQY files hidden within ZIP archives or embedded in PDF documents, while the other campaign used Microsoft Word documents containing malicious macros.

All of these attachments led to the same payload: Marap, a downloader malware that uses a custom application programming interface (API) hashing algorithm, timing checks and media access control (MAC) address comparisons to avoid analysis by security professionals. Marap has the ability to download other modules and payloads, including a fingerprinting plugin that steals and exfiltrates key system information.

Attackers Shift Focus to IQY Files

Marap isn’t the first malware to rely on IQY attachments for distribution. Trend Micro recently discovered a campaign in which Necurs, a botnet that has a history with malicious spam, used IQY file attachments to begin a PowerShell process and thereby download the backdoor FlawedAMMYY. Soon after making that observation, researchers at the Japanese security firm detected the Cutwail botnet leveraging IQY files to target Japanese users with BEBLOH or URSNIF malware.

Security researchers at Barkly noted that malware actors are increasingly turning to IQY files. These attachments appeal to digital attackers because they are capable of bypassing most filters and antivirus software, since Microsoft Excel can legitimately use this type of file format to download web data directly into a spreadsheet.

How Can Financial Companies Defend Against Malicious IQY Files?

Given the growing preference for IQY files among digital attackers, security professionals should update their firewalls and email filtering tools to block these attachments outright. Information security professionals should also use real-time threat intelligence sharing to stay informed of advanced threats like Marap.

Sources: Proofpoint, Trend Micro, Trend Micro(1), Barkly

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