HollowQuill Malware Attacking Government Agencies Worldwide Via Weaponized PDF Documents

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A sophisticated malware campaign dubbed “HollowQuill” has emerged as a significant threat to academic institutions and government agencies worldwide.

The attack leverages weaponized PDF documents disguised as research papers, grant applications, or official government communiques to entice unsuspecting victims into initiating the infection chain.

The malware employs advanced social engineering tactics to increase its success rate, creating convincing decoy documents that appear legitimate to even security-conscious users.

Once opened, these seemingly innocuous PDFs trigger a complex multi-stage infection process designed to evade detection while establishing persistence.

Broadcom analysts have identified this campaign as particularly concerning due to its targeted nature and sophisticated evasion techniques.

Their research indicates the attackers are likely pursuing sensitive government and academic data for espionage purposes.

The attack demonstrates remarkable technical sophistication, beginning with the distribution of malicious RAR archives containing a .NET malware dropper.

This initial compromise leads to deployment of multiple payloads including a legitimate OneDrive application that helps the malware blend into normal system operations.

Infection Mechanism

The HollowQuill infection chain begins when users open seemingly legitimate PDF documents.

Behind the scenes, the initial dropper executes and deploys a Golang-based shellcode loader responsible for memory-based execution of the primary payload, significantly reducing detection rates by traditional security solutions.

This sophisticated mechanism allows attackers to maintain persistence while extracting sensitive information from compromised systems.

// Simplified representation of initial .NET dropper code
public static void DeployPayload() {
    string legitApp = "OneDrive.exe";
    byte[] shellcodeLoader = GetEncryptedPayload();

    // Deploy legitimate application as cover
    File.WriteAllBytes(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) 
        + "\" + legitApp, GetLegitApp());

    // Execute shellcode loader with obfuscated parameters
    ExecuteInMemory(Decrypt(shellcodeLoader, GetSystemKey()));
}

Recommended defenses include disabling office macro scripts, implementing application allowlisting, and monitoring for DNS query anomalies to counter this evolving threat landscape.

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