Threat Actors Use Malicious RMM Tools for Stealthy Initial Access to Organizations

A small increase in targeted cyberattacks that make use of Remote Monitoring and Management (RMM) capabilities that are embedded in PDF documents has been seen by WithSecure.

These campaigns primarily focus on organizations in France and Luxembourg, employing socially engineered emails to deliver innocuous PDFs containing hyperlinks to legitimate RMM installers.

This method effectively circumvents email gateways and endpoint defenses by leveraging trusted, signed executables.

RMM tools, designed for IT administration, serve as potent initial access vectors, enabling adversaries to remotely control systems, disable security controls, escalate privileges, and deploy secondary payloads.

This technique echoes tactics used by ransomware groups like Black Basta, which impersonate support staff to induce RMM installations for ransomware delivery.

Evolving Tactics in Targeted Cyber Campaigns

The observed activity emphasizes the weaponization of benign software, with threat actors adapting RMM usage for persistence and stealth, marking an evolution from broad phishing to precision targeting of high-value sectors such as energy, government, banking, and construction.

The campaigns exhibit geographic specificity, with most incidents in Europe, though sporadic cases extend beyond.

Luxembourg’s high GDP per capita makes it an attractive target for financially motivated actors, suggesting a calculated strategy prioritizing lucrative compromises over volume-based attacks.

According to the report, PDFs are customized to victims’ industries featuring blurred images or sector-specific lures like invoices or contracts to enhance plausibility and prompt clicks.

For example, a Dutch real estate firm was targeted with a PDF in Dutch referencing FleetDeck RMM.

Metadata analysis reveals patterns in PDF authorship, including names like “Dennis Block” and “Guillaume Vaugeois,” generated via tools such as Microsoft Word, Canva, and ILovePDF, indicating efforts to diversify artifacts and evade signature-based detection.

Timeline data from VirusTotal traces RMM abuse back to July 2024, with tools like Atera, Bluetrait, and ScreenConnect deployed via direct or redirected URLs, streamlining infection without post-installation configuration.

Delivery Vectors

Delivery relies on PDFs with embedded direct-download links to RMM vendors’ servers, often spoofed from legitimate domains or impersonating executives to bolster authenticity.

A recent pivot involves abusing Zendesk for PDF distribution through support tickets, bypassing email filters by hosting clean attachments on trusted platforms.

Once installed, RMM agents grant immediate remote access, potentially leading to ransomware or data exfiltration, though no secondary payloads have been confirmed in this cluster.

To mitigate, organizations should enforce application allowlisting to block unauthorized RMM executions, restrict downloads of tools like FleetDeck unless approved, and monitor anomalous process chains such as PDFs spawning browser downloads of MSI/EXE files via EDR solutions.

User education on phishing red flags, including unsolicited IT support requests, remains essential.

This activity underscores the risks of legitimate RMM tools in adversarial hands, facilitating stealthy breaches through socially engineered vectors.

Vigilance against such abuses, particularly in Europe-focused operations, is critical to prevent escalation to advanced threats like those from Conti or BlackCat groups.

Indicators of Compromise (IOCs)

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