Imagine you’re on LinkedIn using your work laptop when a coworker messages you a document for review. You click the attachment — which looks like a standard PDF link — without a second thought. In one click, you’ve handed a hacker the keys to not just your data, but your entire company’s network. 

In today’s era of well-designed social engineering attacks, threat actors often develop new ways to leverage existing attack methods, such as DLL side loading — a bait-and-switch tactic in which a hacker dupes a trusted website or platform into running malicious code. This technique enables an attacker to use legitimate tools such as PDF readers as the delivery mechanism for their malware.

Recently, bad actors have taken DLL Side Loading to social platforms like LinkedIn, which provides them with the ability to attach and send files and links via direct messages, and then side-load malware through the use of a trusted application. Side-loading is far from new, but the way in which hackers are now creatively combining social engineering with messenger-based phishing via prestigious, trusted platforms like LinkedIn creates a growing problem for unsuspecting employees. 

For security leaders, this evolution raises questions about what’s not working with threat detection in the enterprise and how they can give users the tools to recognize and avoid creative attack techniques.

Understanding the Mechanics of Modern DLL Side-Loading

Sideloading is straightforward: attackers slip malicious applications or code into an operating system by disguising them as legitimate files, causing the system to run commands it was never meant to execute. In practice, an attacker might pose as a trusted contact and send what appears to be a harmless PDF link through LinkedIn Messenger. With a single click, the victim can unknowingly grant the attacker access far beyond their own data — potentially exposing sensitive information across the entire organization.

LinkedIn is just one example — and far from the only social media platform that attackers can exploit. Many popular platforms offer messaging features and allow file attachments, making them equally vulnerable targets. While LinkedIn may appear more trusted in professional settings, security leaders must also stay alert to threats that originate on X (formerly Twitter), Facebook Messenger, Telegram, and WhatsApp. Given LinkedIn’s widespread use in the corporate world, it’s understandable why attackers increasingly rely on it as a primary channel for launching phishing campaigns.

The Problem With Legacy EDR Strategies — Reactive Vs. Proactive Infrastructure

It’s critical to consider the context of these side loading attacks successfully evading detection by traditional endpoint security tools (EDR, XDR, MDR), and masking their intent by leveraging legitimate processes. In fact, it’s recently been found that 66% of malware infections are occurring on devices where endpoint protection solutions are already installed.

CISOs and security leaders must carefully audit their security environment and current detection tools, to make sure that endpoints are locked down and protected and are being monitored for risky behavior. While most organizations claim they have “Insert Big Name Endpoint Security Vendor” for their endpoint protection and security, I challenge those companies to reconsider how they look at endpoint security. 

A mature endpoint security strategy requires two complementary components: proactive security and reactive security. Embracing both demands a strategic and cultural shift from traditional security operations. To support this transformation, security leaders are increasingly adopting Unified Endpoint Management and Privileged Access Management (PAM) tools, which emphasize strong security and data hygiene rather than relying solely on incident response. These tools can prevent malicious DLLs from loading by blocking unnecessary or risky application privileges, strengthening the overall security environment.

The Awareness Gap: Building A Threat-Aware Security Culture

Despite the extensive security awareness training many organizations provide, major breaches and compromises continue to occur. This reveals a persistent gap between how quickly threats are evolving and how well employees understand and recognize them.

A critical layer of building a proactive (vs. reactive) security strategy starts the organization’s people. Security leaders must strive to build a threat-aware culture that prioritizes constant education and upskilling around AI-powered and developing scams. This is not a ‘one-size-fits-all’ strategy — organizations must closely audit which specific threats are facing their employees (based on industry, workplace platforms in use, remote vs hybrid ecosystems etc.) to significantly reduce this type of behavior threat actors are capitalizing on. As these scams are behavior-based, the human element in threat prevention is critical to prioritize, directly contributing to prevention of these scams if employees are threat-aware. 

Phishing, sideloading, and social engineering aren’t new — but the rise of advanced social threats like LinkedIn Messenger sideloading reinforces the need for a zero trust mindset. Anyone on social platforms should be treated as unknown and untrusted. To prevent attacks like these, security leaders must prioritize proactive tools such as PAM and work to close the organization’s cyber awareness gap, protecting both their data and their bottom line.