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Introduction:
A dangerously advanced Windows malware campaign has surfaced, catching even seasoned cybersecurity experts off guard. Recently uncovered by the FortiGuard Incident Response Team, this elusive threat operates entirely in memory, leaving virtually no trace on disk. By corrupting its own executable headers and embedding sophisticated encryption, it stealthily maintains control over infected systems while bypassing traditional forensic tools. The attack, cleverly disguised under the legitimate Windows process dllhost.exe, took weeks to uncover due to its level of technical precision. As we break down the key aspects of this malware, it becomes clear we are dealing with a new breed of threats designed for maximum persistence and minimal visibility.
Overview of the Attack (Digest – ~30 lines):
Fortinet’s security team has revealed a highly evasive Remote Access Trojan (RAT) that infected Windows systems by using advanced in-memory execution. First detected as a 64-bit process inside dllhost.exe, the malware resisted direct extraction, forcing investigators to analyze a massive 33GB memory dump. Within the dump, they discovered that both the DOS and PE headers had been intentionally zeroed out. This effectively prevented standard memory-to-disk reconstruction and thwarted traditional reverse engineering methods.
To understand and recreate the attack, analysts mirrored the compromised environment, manually allocating memory in a clean dllhost.exe and using tools like IDA Pro and Volatility. Since the PE headers were missing, they manually identified the malware’s entry point by analyzing assembly code patterns. They also had to rebuild the Import Address Table from scratch, mapping Windows API addresses and restoring global variable memory segments to their correct locations.
The malware decrypted its Command-and-Control (C2) settings during execution, revealing it communicated over rushpapers.com using TLS port 443. But even standard encryption wasn’t enough—this threat layered a custom XOR-based algorithm on top of TLS, masking payload data and making deep packet inspection nearly impossible.
The final payload revealed a full-featured RAT with capabilities such as screen capturing, embedded TCP server spawning, and control over local Windows services via legitimate APIs. All functions blend with native Windows behavior, making detection extremely challenging. Analysts captured initial network handshakes and profiled data that included OS details sent to attackers. The custom XOR encryption used variable-length keys and recursive operations, adding another layer of obfuscation.
What Undercode Say:
This attack highlights a seismic shift in the evolution of malware engineering. By discarding conventional PE header structures and moving operations fully into volatile memory, attackers are deliberately steering away from signatures and disk-based detections. This represents a new phase where malware doesn’t just hide—it blends.
The use of dllhost.exe, a legitimate and commonly running Windows process, as a vessel, is a strategic move. This choice reduces suspicion and allows the malware to piggyback off system trust. Traditional antivirus tools largely rely on static analysis, so the zeroing out of PE headers is a brilliant, albeit malicious, innovation. This technique makes it almost impossible to reconstruct a working sample from memory dumps unless you have expert-level reverse engineering skills.
What’s even more troubling is the malware’s ability to self-replicate a secure communication channel through a double layer of encryption: TLS for standard security and XOR to mask the application-layer content. This means even if defenders manage to intercept network traffic, decrypting it would require knowing the custom XOR algorithm and dynamic key generation mechanisms.
The command-and-control model using TLS WebSocket traffic demonstrates an effort to stay hidden in plain sight. Many enterprise firewalls and IDS systems overlook WebSockets unless explicitly configured. Combining that with standard ports like 443, attackers successfully blend into everyday HTTPS traffic.
By employing Windows Service Control Manager APIs and creating a TCP server for remote control, the malware morphs from a passive data thief into an active system manipulator. The multi-threaded session handling also implies it can scale across targets without performance bottlenecks.
From an incident response perspective, the fact that a 33GB memory dump was needed just to isolate and examine the malware underscores the complexity and seriousness of this attack. It places tremendous pressure on security teams to enhance real-time memory monitoring and deploy behavior-based detection mechanisms.
This case is a clarion call for updating defensive strategies. Signature-based AVs are becoming obsolete. Detection now demands memory forensics, API behavior analysis, and encrypted traffic inspection. Organizations must assume that tomorrow’s threats won’t leave footprints. Instead, they’ll live in memory, speak through encrypted tunnels, and cloak their actions with legitimate Windows APIs.
Fact Checker Results:
🔍 Confirmed malware operates entirely in memory, using zeroed PE headers.
🧪 Encrypted TLS WebSocket traffic with custom XOR layer validated by Fortinet’s forensic tools.
🧠 Behavioral analysis confirms full RAT capabilities, including TCP server and system service control.
Prediction:
This malware marks a turning point in cyberattacks. Expect to see more threats leveraging headerless execution, in-memory persistence, and encrypted multi-layered C2 channels. Attackers are moving toward “living off the land” tactics, and defenders must pivot to real-time behavioral analysis, memory inspection, and encrypted traffic analysis to stay ahead. Security vendors may soon adopt AI-driven memory pattern recognition tools to detect such sophisticated threats before damage occurs.
References:
Reported By: cyberpress.org
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