Coyote Malware Launches Stealthy Attack on Windows Systems via LNK Files

FortiGuard Labs has issued a high-severity alert regarding the Coyote Banking Trojan, a sophisticated malware targeting Microsoft Windows users.

Over the past month, researchers have identified malicious LNK files employing PowerShell commands to execute scripts and connect to remote servers, initiating a multi-stage attack.

The primary objective of this Trojan is to harvest sensitive information from over 70 financial applications and numerous websites, predominantly affecting users in Brazil.

The attack begins with an LNK file that executes a PowerShell command to connect to a remote server.

This command initiates the download and execution of additional malicious scripts.

By analyzing metadata embedded within the LNK files, such as the “Machine ID” and MAC addresses, researchers traced connections to other malicious files associated with the Coyote Trojan.

Malware Mechanisms

The attack progresses through several stages, utilizing a combination of loaders, shellcode, and registry modifications.

A DLL file named “bmwiMcDec” acts as a loader, injecting malicious payloads into targeted processes using functions like VirtualAllocEx and WriteProcessMemory.

The injected code employs Donut, a tool for decrypting and executing Microsoft Intermediate Language (MSIL) payloads.

Once decrypted, the MSIL payload establishes persistence by modifying the Windows registry.

It replaces existing PowerShell commands with new entries pointing to Base64-encoded URLs that download and execute additional malware components.

The Trojan also collects system information such as machine names, usernames, operating systems, and installed antivirus software and transmits it to remote servers after encoding it in Base64.

The final payload includes the main Coyote Banking Trojan, which expands its target list to over 1,000 websites and 73 financial agents.

It monitors active windows for access to targeted sites and communicates with command-and-control (C2) servers via port 443.

Depending on instructions from the C2 server, the Trojan can perform various actions, such as keylogging, taking screenshots, displaying phishing overlays, or manipulating user-visible windows.

Implications for Financial Cybersecurity

The Coyote Banking Trojan represents a significant threat to financial cybersecurity due to its advanced techniques and ability to adapt its targets.

Its capacity to monitor user activity and steal sensitive credentials highlights the importance of robust security measures for both individuals and organizations.

Fortinet’s security solutions provide protection against this malware.

The FortiGuard Antivirus service detects and blocks related threats under signatures like “LNK/Agent.D!tr.”

Additionally, Fortinet’s Web Filtering Service blocks access to known C2 servers associated with the attack.

Users are encouraged to keep their security systems updated and undergo cybersecurity training to identify potential threats.

This incident underscores the evolving nature of cyberattacks targeting financial institutions and the critical need for proactive defenses against multi-stage malware campaigns.

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