Unmasking the Invisible Threat: How Direct Syscalls Evade Detection and What Your Business Can Do About It

Imagine a burglar bypassing all your home’s security systems—not by breaking them, but by finding a path that your alarms don’t even watch. That’s what cyber attackers are doing with direct syscalls, a stealth technique that can bypass many EDR (Endpoint Detection and Response) tools without raising a single alert.

In this article, we’ll break down what direct syscalls are, why they’re such a big deal for companies of all sizes, and how Cortex XDR has risen as a leading force in detecting and stopping these silent threats.

What Are System Calls, and Why Do They Matter?

Every program on Windows that needs to talk to the operating system—say, to access a file or allocate memory—uses a system call (syscall). Normally, these syscalls are made through user-mode libraries like ntdll.dll that EDRs can monitor.

Most EDR solutions hook into these user-mode functions to track what’s happening. When a program makes a call like CreateFileW, it travels through known DLLs, where EDRs set traps to see what’s being done.

How Attackers Use Direct Syscalls to Slip Past Security

Now here’s the trick: attackers bypass those traps by not using the official doorways. They use direct syscalls—custom-implemented system call instructions that jump straight to the Windows kernel. This allows them to:

• Avoid the hooks set by EDRs in user-mode DLLs
• Evade detection while performing malicious actions like process injection
• Leave minimal traces that could alert traditional monitoring tools

And that’s not all. Sophisticated attackers pair direct syscalls with methods like manual DLL loading or DLL cloning to ensure they never touch anything an EDR might watch.

Cortex XDR: A Different Breed of Detection

So how do you stop something designed to be invisible? Cortex XDR doesn’t just look at the surface. It dives deep, intercepting syscalls from the kernel itself. That’s like placing your security cameras inside the vault, instead of just at the front door.

Here’s how it works:

• Kernel-Level Interception: Cortex XDR captures syscalls as they enter the kernel, regardless of where they came from.
• ImageTracker Technology: It traces the source of each syscall using a proprietary module that tracks all loaded code, identifying if the syscall came from a legitimate DLL or rogue shellcode.
• Behavioral Analytics Engine: Cortex XDR uses AI-powered analytics to determine if a syscall is suspicious based on context—like frequency, origin, and known behavior of the process.

Real-World Case: Lumma Stealer

Cortex XDR’s capabilities were proven in action against Lumma Stealer, a notorious info-stealing malware. The malware:

• Used an expired certificate to look trustworthy
• Extracted syscall indexes dynamically
• Bypassed standard API calls entirely
• Performed memory injection into other processes via direct syscalls

Cortex XDR detected this behavior not by spotting a signature, but by recognizing that a process not known for syscall activity suddenly started making a suspicious number of direct calls from an unusual memory region.

Why This Matters for Your Business

Whether you’re a small startup, a mid-sized organization, or a global enterprise, the reality is the same: modern cyber threats don’t play by the rules. Relying on user-mode EDRs alone is like locking your front door while leaving the back wide open.

With techniques like direct syscalls becoming more common in malware-as-a-service toolkits, proactive detection and behavioral analysis are no longer optional—they’re critical.

Final Thoughts

Cybersecurity isn’t just about reacting to threats anymore. It’s about anticipating how attackers evolve and making sure your defenses are a step ahead.

Direct syscall detection is one of the clearest frontiers in today’s security battle—and Cortex XDR is equipped to lead that charge.