The IRS Doc Malware is a low-severity malware threat primarily delivered via spearphishing attachments, specifically malicious documents (maldocs). The attack chain begins with a targeted spearphishing email containing a weaponized document designed to exploit user trust and induce execution. Upon opening the document, the malware leverages scripting techniques, including PowerShell commands and command-line interface execution, to run malicious payloads. Persistence is achieved through modification of registry run keys or placing scripts in startup folders, ensuring the malware executes on system reboot. The malware also utilizes Background Intelligent Transfer Service (BITS) jobs to facilitate stealthy and reliable data transfer or command execution. Network communication is conducted over commonly used ports and employs standard cryptographic protocols to evade detection and secure command and control (C2) communications. The malware's tactics align with several MITRE ATT&CK techniques such as T1193 (spearphishing attachment), T1059 (command-line interface), T1086 (PowerShell), T1064 (scripting), T1060 (registry run keys/startup folder), T1197 (BITS jobs), T1043 (commonly used port), and T1032 (standard cryptographic protocol). No specific affected software versions are identified, and no patches are available, indicating the malware exploits social engineering and scripting rather than software vulnerabilities. There are no known exploits in the wild beyond the spearphishing vector, and no detailed indicators of compromise (IOCs) are provided. The overall impact is limited by the low severity rating, but the malware's use of multiple persistence and evasion techniques makes it a credible threat in targeted environments.

For European organizations, the IRS Doc Malware poses a risk primarily through targeted spearphishing campaigns that can lead to unauthorized access, data exfiltration, or lateral movement within networks. The use of PowerShell and scripting can bypass traditional signature-based defenses, potentially compromising confidentiality and integrity of sensitive data. The persistence mechanisms enable long-term footholds, increasing the risk of prolonged espionage or data theft. While the malware does not appear to cause direct availability impacts, the stealthy communication and use of standard protocols complicate detection and response efforts. European entities handling sensitive financial, governmental, or personal data are particularly at risk, as attackers may leverage this malware to gain initial access or establish command and control channels. The low severity rating suggests limited widespread impact but does not preclude significant damage in targeted attacks, especially if combined with other attack vectors or follow-on exploitation.

European organizations should implement targeted defenses against spearphishing and maldoc threats. This includes advanced email filtering with attachment sandboxing to detect malicious documents before delivery. User awareness training focused on recognizing spearphishing attempts and suspicious attachments is critical. Endpoint detection and response (EDR) solutions should be configured to monitor and alert on suspicious PowerShell activity, command-line executions, and modifications to registry run keys or startup folders. Monitoring for unusual BITS job creations and network traffic over commonly used ports with encrypted protocols can help identify stealthy C2 communications. Implementing application whitelisting to restrict execution of unauthorized scripts and enforcing least privilege principles reduces the attack surface. Regularly auditing persistence mechanisms and network connections can detect anomalies early. Since no patches exist, emphasis on detection and prevention is paramount. Incident response plans should include procedures for maldoc infections and lateral movement containment.