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Phishing Emails Deliver Amadey Malware to U.S. Taxpayers

A recently observed phishing campaign is targeting taxpayers in the United States in an attempt to infect their machines with a piece of malware named Amadey, Cofense security researchers have discovered.

A recently observed phishing campaign is targeting taxpayers in the United States in an attempt to infect their machines with a piece of malware named Amadey, Cofense security researchers have discovered.

Relatively new and fairly simple, the Amadey botnet is available for hire for cybercriminals. One of the threat groups to have used the botnet is TA505, which leveraged it to distribute the FlawedAmmy RAT and email stealers.

The phishing campaign, Cofense explains, employs emails purporting to be from the Internal Revenue Service (IRS) and claiming that the recipient is eligible for a tax refund. The message also presents a “one time username and password” and urges the user to click the “Login Right Here” button.

The button, however, is an embedded hyperlink that redirects to hxxp://yosemitemanagement[.]com/fonts/page5/, where a fake IRS login page is displayed, asking the user to enter the one-time password, the researchers reveal.

Following the login, the user is informed of a pending refund and is asked to download a document, print and sign it, then either email it or upload it to the portal. If the user attempts to download the document, they are served a ZIP file that contains a Visual Basic script dropper.

Highly obfuscated and encrypted, the VBScript was designed to drop an executable file that proceeds to install another executable and run it. To achieve persistence, Amadey sets up its own registry to add its installation folder to the Windows startup sequence.

Immediately after installation, the bot beacons to the command and control (C&C) server, sending system diagnostic information and then awaiting further instructions. Amadey connects via HTTP on port 80 to multiple C&C servers, the researchers discovered.

Information the bot sends back to the server includes a unique identifier of the infected system, the malware variant, operating system, antivirus software, system name, and username.

Related: Smominru Botnet Infects Thousands of Hosts Daily

Related: Crypto-Mining Botnet Implements BlueKeep Scanner

Related: GAO Makes Recommendations to Improve Security of Taxpayer Data

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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