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Sophisticated Threat Emerges from the Cloud
A powerful new malware campaign has emerged from the shadows, revealing a growing cyber threat trend: abusing trusted cloud infrastructure to launch stealthy attacks. Dubbed SERPENTINECLOUD, this malware leverages Cloudflare Tunnel services to conduct a multi-layered Python-based attack on Windows systems. What makes it particularly alarming is how well it hides its operations within legitimate tools and services—camouflaging itself behind encrypted traffic and trusted domains, while deploying advanced in-memory payloads that sidestep traditional antivirus detection.
First spotted in the US, UK, Germany, and across Europe and Asia, SERPENTINECLOUD represents a new level of sophistication in cyberattack strategies. By using encrypted channels and temporary domains on Cloudflare’s infrastructure, threat actors have essentially hijacked a developer-friendly toolset to deliver weaponized payloads with surgical precision. The threat has been active in various regions, and analysts are still working to trace its origins, though English-language code hints at a focus on Western targets.
Cloud Infrastructure Becomes a Weaponized Shield
The SERPENTINECLOUD campaign begins with phishing emails—a tried-and-true method—but with modern refinements. These emails deliver zipped attachments that appear to be routine invoices or payment documents. Once the file is opened, a hidden .lnk shortcut (with a fake PDF icon) quietly launches Windows utilities like cmd.exe and robocopy to download malicious scripts.
The initial scripts are pulled from ephemeral Cloudflare Tunnel subdomains, making takedown efforts almost impossible. These subdomains are disguised using trycloudflare[.]com links, which benefit from Cloudflare’s encryption and trusted status in enterprise environments.
Upon execution, the .lnk file triggers a chain of loaders:
A `.wsf` file pulls down a `.bat` script.
The .bat script is deeply obfuscated to deter reverse engineering.
It checks for antivirus tools, displays fake PDFs as distractions, then downloads a ZIP archive containing the Python-based malware.
This ZIP file includes the Python runtime, various loader scripts, and payloads that inject shellcode directly into memory, bypassing disk-based defenses. One such script uses Early Bird APC injection, sneaking code into processes like notepad.exe before they fully launch—an advanced evasion technique.
Stealth and Persistence Are Top Priorities
The attackers use tools like Donut (for .NET/PE in-memory loading) and Kramer (for Python obfuscation), both designed to avoid detection and forensic recovery. Payloads are encrypted using RC4 and XOR, then decrypted at runtime using Python’s ctypes module, allowing direct interaction with Windows APIs.
Persistence is achieved by planting additional scripts in Windows startup directories, ensuring the malware restarts on every user login. Some scripts even prevent the system from sleeping or becoming idle—minimizing interruptions during payload deployment.
Cloudflare Tunnel, typically used by developers to expose local environments securely, has now been hijacked for malicious purposes. The combination of SSL/TLS encryption, CDN fronting, and temporary subdomain generation gives attackers a disposable but effective infrastructure that security tools rarely flag.
To fight back, experts recommend:
Training users on phishing awareness
Making file extensions visible
Monitoring for abnormal script execution
Watching network traffic to domains like `trycloudflare[.]com`
Using behavior-based detection for suspicious persistence and process injection activities
Attribution remains unclear, but the campaign’s precision, obfuscation, and targeting suggest a well-resourced threat actor refining scalable, cloud-based attack chains with global reach.
What Undercode Say:
The Evolution of Cloud-Based Threats
The SERPENTINECLOUD campaign is not just another malware incident—it signals a broader evolution in how cybercriminals are adapting to the changing technological landscape. Traditionally, attackers relied on shady hosting services or compromised machines for command-and-control. Today, they’re repurposing legitimate cloud infrastructure to blend in with regular traffic.
This approach offers significant advantages:
Trust evasion: Services like Cloudflare are rarely blocked, allowing malware to bypass perimeter defenses.
Ephemeral hosting: The use of throwaway subdomains makes blacklisting efforts a game of whack-a-mole.
Encrypted tunnels: Security products often can’t inspect the content within these tunnels due to end-to-end encryption.
Python as a Double-Edged Sword
Python’s flexibility and readability have made it a favorite for developers—but also for attackers. With Python, malware developers can rapidly prototype complex attack chains. The inclusion of the portable Python runtime in the payload ensures compatibility, even on systems without Python installed.
Using ctypes to interact with low-level Windows APIs demonstrates a deep understanding of both the language and the target platform. Combine this with memory-only execution and you get a malware chain that leaves virtually no forensic trail.
Fileless Tactics and Multi-Stage Loaders
SERPENTINECLOUD takes a modular, multi-stage approach, which allows attackers to control each phase of the infection chain:
1. Gain access via phishing.
2. Use native tools to avoid detection.
3. Gradually escalate by deploying loaders.
- Inject code into memory to avoid writing to disk.
This fileless model is becoming increasingly common, and it signals the diminishing usefulness of traditional signature-based antivirus software.
Obfuscation as a Defense
The use of Donut and Kramer highlights a broader shift toward defensive coding on the offensive side. Attackers now use the same obfuscation techniques employed by developers trying to protect intellectual property. In malware, however, the goal is to resist both static and dynamic analysis.
This also presents major challenges for malware analysts, who must now deal with encoded payloads, nested scripts, and staged decryption, often requiring full behavioral execution to understand functionality.
Cloudflare’s Dilemma
While Cloudflare has done much to secure the web, its tools can also be misused. The trycloudflare.com subdomains offer fast, temporary URLs that are ideal for spinning up quick test environments—but that very convenience is now being turned into a security risk. The company finds itself in a difficult position, needing to balance developer needs with abuse prevention.
Enterprises must proactively monitor for traffic to development-centric domains, and not blindly trust them just because of their reputation.
🔍 Fact Checker Results:
✅ Cloudflare Tunnels are confirmed to be used in malware distribution in this campaign
✅ Python scripts are executing in-memory shellcode, evading traditional antivirus detection
✅ Fileless malware and multi-stage loaders are accurate descriptions of the SERPENTINECLOUD architecture
📊 Prediction:
Expect an increase in malware campaigns abusing cloud infrastructure, especially services like Cloudflare Tunnel and Ngrok. Cybersecurity vendors will need to develop behavior-based solutions capable of analyzing encrypted traffic patterns and detecting script-based persistence. As fileless attacks grow more common, endpoint protection platforms must evolve or risk becoming obsolete. Attackers are adapting fast, and the defenders must now rethink their strategy—starting at the cloud.
References:
Reported By: cyberpress.org
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