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Introduction: A Quiet Digital War That Leaves No Footprints
In the shadows of ongoing cyber conflict, a new wave of stealth-driven malware has emerged, reshaping how espionage operates inside Ukrainian networks. This campaign, attributed to the Russian state-linked hacking group Gamaredon, demonstrates a disturbing evolution: malware that doesn’t just infiltrate systems, but disappears into the architecture of Windows itself. Discovered by analysts at Sekoia, the worm exploits hidden Windows file features, living almost invisibly while spreading laterally across critical infrastructure.
What makes this operation particularly alarming is not just its origin, but its design philosophy. It is built for persistence, silent propagation, and long-term espionage—turning compromised systems into quiet intelligence outposts.
Summary: From WinRAR Exploit to Fileless Digital Infection Chain
The attack chain begins with a deceptive XHTML file that delivers a malicious archive exploiting a vulnerability tracked as CVE-2025-8088. Once opened, it triggers a hidden payload that installs itself deep within the Windows startup process.
From there, the malware evolves into a fileless VBScript-based worm, dramatically reducing forensic traces on infected machines. This shift marks a significant upgrade from earlier tools used by Gamaredon, which were far more dependent on visible disk artifacts.
The campaign ultimately results in a stealthy, self-propagating worm capable of spreading through USB drives, network shares, and system persistence mechanisms—while remaining almost invisible to standard detection tools.
Initial Breach: The WinRAR Trap That Opens the Door
The intrusion begins with social engineering and exploitation combined. Victims unknowingly open a booby-trapped XHTML file that silently drops a compressed archive.
Inside this archive lies the exploit targeting CVE-2025-8088, which allows attackers to place malicious files outside intended directories. The payload installs an HTA file in the Windows Startup folder, ensuring execution upon reboot.
A decoy PDF is also deployed, acting as psychological camouflage—keeping the victim unaware while the system quietly becomes compromised.
GammaWorm Emerges: Malware Hidden Inside Windows Memory Structures
At the core of this operation is the worm identified as GammaWorm. Rather than writing visible files to disk, it embeds its components into NTFS Alternate Data Streams, a rarely inspected Windows feature that allows data to exist “behind” normal files.
This technique makes detection extremely difficult, as traditional file system views do not reveal hidden streams.
GammaWorm also establishes persistence via scheduled tasks disguised as routine system maintenance. Registry modifications further suppress file visibility, reinforcing its stealth layer.
Propagation Phase: Spreading Through USBs and Network Lures
Once active, the worm begins lateral movement across connected systems. USB devices and network shares become vectors for expansion.
It hides legitimate folders and replaces them with malicious shortcut files containing attention-grabbing Ukrainian-language names designed to provoke user interaction.
This blend of psychological manipulation and technical stealth makes the worm particularly effective in human-centered environments such as government offices and infrastructure systems.
Command and Control: Living Off Telegram and Cloudflare
For communication, GammaWorm avoids traditional malicious servers. Instead, it retrieves command-and-control data from legitimate platforms like Telegram and Cloudflare.
These services act as “dead drop resolvers,” allowing attackers to rotate infrastructure without raising immediate suspicion. Extracted data is stored in the Windows registry, ensuring survival even after partial cleanup attempts.
This architecture transforms infected machines into resilient backdoors capable of executing remote instructions indefinitely.
Attribution and Strategic Focus: Ukraine Under Persistent Targeting
Investigators confirm that this campaign aligns with the long-standing operations of Gamaredon, which is widely assessed to operate under or alongside the Russian FSB.
The group’s targeting remains heavily concentrated on Ukrainian government institutions, military networks, and critical infrastructure. The goal is not disruption alone, but sustained intelligence gathering and long-term access.
Defense Reality: Why Cleaning Is Not Enough
Security researchers at Sekoia warn that traditional cleanup is often insufficient. Because the worm continuously pulls fresh payloads from external resolvers, partial removal can trigger automatic reinfection.
As a result, the recommended remediation strategy is severe but necessary: full system reimaging.
Additionally, organizations are urged to update WinRAR to version 7.13 or later to patch CVE-2025-8088 and eliminate the initial entry point.
What Undercode Say:
This campaign represents a shift from visible malware to architecture-level invisibility
NTFS Alternate Data Streams are still underused in modern threat detection models
Gamaredon’s evolution shows increasing operational maturity and automation
Fileless VBScript execution reduces forensic recovery chances significantly
USB propagation remains effective despite modern endpoint security systems
Psychological naming in shortcuts increases human interaction probability
Legitimate services like Telegram are becoming C2 infrastructure substitutes
Cloudflare abuse highlights the dual-use nature of modern internet services
Dead Drop Resolvers create resilient but opaque command structures
Registry-based persistence complicates memory-only cleanup approaches
WinRAR vulnerabilities remain a recurring entry point in espionage campaigns
XHTML-based delivery shows continued use of legacy file formats in attacks
Decoy documents remain highly effective against non-technical users
Fileless malware trends indicate declining reliance on disk artifacts
Scheduled task disguise mimics legitimate system behavior effectively
Ukrainian-language lure files suggest localized psychological targeting
Network share propagation mirrors traditional worm behavior but stealthier
Security tools relying on file scanning alone are insufficient
Kernel-level monitoring is increasingly necessary for detection
Attackers are blending cyber espionage with social engineering tactics
Persistence mechanisms now span registry, tasks, and hidden streams
Malware ecosystems are increasingly modular and reusable
Infrastructure decentralization makes takedown efforts less effective
Attribution remains strong but operational proof is still indirect
State-linked actors are prioritizing stealth over destructive payloads
Long-term access is more valuable than immediate disruption
Multi-stage infection chains reduce detection windows
Endpoint detection must evolve toward behavioral analysis
Legacy Windows features remain attack surface hotspots
Cyber warfare increasingly mirrors intelligence tradecraft
Hidden stream abuse is still underrepresented in enterprise defense
Attackers are leveraging trust in legitimate platforms
Payload rotation ensures resilience against partial mitigation
USB-based spread remains relevant in offline-critical environments
Malware design now prioritizes survivability over speed
Human interaction remains the weakest security layer
Defensive patching cycles lag behind exploit discovery timelines
Cross-platform infrastructure abuse is becoming standard
Cyber espionage campaigns are increasingly automated
The boundary between malware and living system processes is fading
❌ The report is consistent with known behaviors of state-linked espionage groups, but specific CVE-2025-8088 attribution to multiple actors cannot be independently confirmed in public datasets.
✅ NTFS Alternate Data Streams are a documented Windows feature commonly abused in stealth malware operations.
❌ Full attribution to Gamaredon under FSB control is widely assessed but not officially publicly proven beyond intelligence community reporting.
Prediction:
(+1) Increased adoption of fileless malware techniques will make endpoint detection increasingly dependent on behavioral AI systems rather than signature-based tools 😐
(+1) Exploitation of legitimate platforms like Telegram and Cloudflare will expand as attackers seek infrastructure blending
(-1) Organizations relying solely on antivirus and patch management will continue to suffer persistent infiltration incidents without full visibility
Deep Analysis: System-Level Exposure and Defensive Commands
Linux (Detection & Investigation)
find / -type f -exec grep -i "Alternate Data Stream" {} \;
strings suspicious_file | less
ls -laR /mnt/usb/
auditctl -w /etc/passwd -p wa
Windows (Forensics & Cleanup)
Get-Item -Path C:\ -Stream
Get-ScheduledTask | where {$_.TaskPath -like ""}
reg query HKCU\Software\Microsoft\Windows\CurrentVersion\Run
wmic startup list full
macOS (Cross-Check Persistence Indicators)
launchctl list ls -la ~/Library/LaunchAgents log show --predicate 'eventMessage contains "suspicious"' --last 1d
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References:
Reported By: www.infosecurity-magazine.com
Extra Source Hub (Possible Sources for article):
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