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Sophisticated Threat Hides Behind Innocent Scripts
A new malware campaign is making waves in the cybersecurity world, leveraging obfuscated Visual Basic Script (VBS) files to silently infiltrate systems and deploy remote access trojans (RATs). Operating across at least 16 open directories, the campaign demonstrates advanced evasion techniques and a meticulous multi-stage infection chain. Its architecture centers on stealth, modularity, and resilient command-and-control (C2) infrastructure, targeting unsuspecting users with cleverly masked scripts and payloads hidden in common formats like JPEGs or text files.
Widespread Infection Through Multi-Stage Deployment
The attack begins with VBS files like “sostener.vbs” serving as the initial point of entry. These scripts are deceptively large, often over 2MB, filled with obfuscated junk to deter reverse engineering. When executed, the VBS dropper decodes an embedded base64 payload in memory and spawns a PowerShell script — a crucial pivot point in the attack. This script then connects to various servers to retrieve second-stage components, which may be concealed within JPEGs on public platforms or disguised using techniques such as reversed strings and further base64 encoding. These payloads can reside on services like gofile.io, paste.ee, or cdn.tagbox.io, helping the threat actors stay under the radar.
In the third and final stage, the PowerShell-downloaded injector runs the payload — a RAT like Remcos, LimeRAT, AsyncRAT, or DCRat — directly in memory. This in-memory execution bypasses traditional disk-based detection mechanisms, making it significantly harder for antivirus software to detect and neutralize the threat. The use of Bitbucket repositories and public code-sharing platforms for hosting malware binaries adds another layer of deception and accessibility for the attackers.
The campaign’s infrastructure is notably robust. It uses the DuckDNS dynamic DNS service to manage a wide pool of domains that constantly rotate IPs, making takedown efforts and tracking incredibly difficult. Threat actors also employ VPNs and port-forwarding services to hide their true server locations. Multiple indicators of compromise (IOCs), including specific domain names, TLS certificate fingerprints, hashes for both RATs and droppers, and even IP addresses used in the attacks, have been identified.
Attribution data suggests potential links to the Colombian threat group APT-C-36, also known as “Blind Eagle.” A threat actor going by the alias “Shadow GRT” has been connected to several payloads involved in the campaign. While conclusive attribution remains elusive due to the open and decentralized nature of the infrastructure, similarities in tactics and tools reinforce suspicions of APT-C-36 involvement.
The campaign represents a potent blend of deception, scalability, and persistence. By combining dynamic script execution, clever payload delivery mechanisms, and resilient infrastructure, the threat actors are able to evade detection while maintaining control over infected systems. It’s a stark reminder of how threat landscapes continue to evolve with increasing technical sophistication.
What Undercode Say:
Modular Payloads Signal a Shift Toward Dynamic Malware Architectures
This malware campaign is a textbook example of how modular design is being leveraged to evade detection. By separating each functional stage — from initial dropper to final RAT deployment — the attackers gain maximum control over every step of infection, all while reducing the risk of detection at any single point. The ability to generate PowerShell scripts dynamically in memory and execute them without writing to disk marks a major advancement in fileless malware operations.
Obfuscation at Scale: The New Norm in Script-Based Attacks
The campaign’s reliance on heavily obfuscated VBS scripts shows that classic scripting languages are far from obsolete. Attackers are now using massive file sizes loaded with junk data to hinder analysis, then embedding base64 payloads that decode on execution. These techniques make sandboxing and reverse engineering far more difficult and time-consuming for defenders.
Cloud and CDN Abuse Is Reaching a Critical Mass
The misuse of trusted platforms like Bitbucket, Internet Archive, and paste.ee is particularly alarming. These services, which are usually considered benign, offer excellent cover for malware hosting. The use of disguised URLs and public cloud platforms to distribute payloads shows how attackers continue to exploit legitimate infrastructure to carry out malicious objectives without raising immediate red flags.
Resilient Infrastructure Undermines Traditional Threat Tracking
The widespread use of DuckDNS dynamic DNS services and port forwarding makes this campaign extremely resilient. Even if one C2 server is taken down, others pop up instantly using new IP addresses and ports. The infrastructure is decentralized enough to remain operational even under active investigation, which is especially concerning from a defensive standpoint.
APT-C-36 Fingerprints Are Present but Attribution Is Cautious
Shadow GRT’s digital footprint and the techniques used point toward the Colombian cyber espionage group Blind Eagle. However, the open infrastructure means attribution must remain cautious. It’s possible that other actors are copying the playbook or repurposing parts of this toolkit, which has been seen in past cyber campaigns where tools leak or get sold on the dark web.
RAT Selection Reveals Broad Operational Goals
The diversity of deployed RATs — including Remcos, LimeRAT, AsyncRAT, and DCRat — indicates a wide range of potential use cases, from espionage to financial theft to persistent surveillance. These RATs offer modular plugins, screen capture, keylogging, file exfiltration, and system control, making them ideal for long-term campaigns targeting both organizations and individuals.
Strategic Use of Obfuscation Hinders Attribution and Forensics
By using layered obfuscation across all stages, from VBS to PowerShell to encoded URLs, the campaign is designed to frustrate forensic analysis. Each decoding operation happens only in memory, leaving minimal trace on disk. Even if one stage is discovered, it reveals little about the final payload or operator behind the scenes.
Threat Actors Leverage Open Directories as Trojan Horses
Open directories serve as easy-access launchpads for distributing malware. They’re rarely monitored and often overlooked, making them a perfect cover for malicious scripts. The fact that this campaign spans at least 16 such directories suggests a strategy of mass exposure, possibly targeting multiple regions or sectors simultaneously.
Evidence of Tactical Evolution Among Threat Groups
The sophistication of this campaign, particularly its infrastructure design and delivery mechanisms, indicates that threat actors are rapidly adapting to modern defenses. Static signatures and domain blacklists are proving ineffective. Cybersecurity tools must evolve to detect behavior patterns and analyze traffic anomalies in real-time to stay ahead.
Implications for Global Cyber Defense
This campaign should be a wake-up call for cybersecurity professionals and organizations globally. The ease with which the attackers bypass traditional defenses using basic scripting tools is a clear indication that perimeter security and endpoint protection alone are not sufficient. A layered defense with behavioral analytics, memory scanning, and threat intelligence integration is now essential.
🔍 Fact Checker Results:
✅ Obfuscated VBS scripts with PowerShell payloads confirmed in active campaigns
✅ Remcos, AsyncRAT, and similar RATs matched with hashes and distribution methods
✅ Use of DuckDNS, Bitbucket, and paste.ee aligns with IOC data from Censys and VirusTotal
📊 Prediction:
🎯 Expect further evolution of this malware framework, possibly integrating AI-driven payloads or advanced anti-analysis techniques
💥 Target range will likely expand to include high-value corporate and governmental systems across Latin America and Europe
🧠 Defensive strategies must adapt quickly, focusing on in-memory execution detection and proactive IOC monitoring for open directory abuse
References:
Reported By: cyberpress.org
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