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Introduction: A Familiar Threat Reinvents Itself
For more than a decade, the Russia-linked cyber espionage group known as Gamaredon has relentlessly targeted Ukrainian institutions, government agencies, military organizations, and critical infrastructure. Security researchers have tracked the group since 2014, watching it evolve from using basic, publicly available malware into one of the most persistent and adaptive cyber-espionage operations active today.
A recent investigation by cybersecurity company Sekoia has revealed what may be the group’s most sophisticated attack chain to date. Using advanced threat hunting techniques powered by YARA detection rules, researchers uncovered a highly modular malware ecosystem designed to establish access, maintain persistence, evade forensic investigations, and continuously deliver malicious payloads.
What makes this campaign particularly alarming is not just the malware itself, but the architecture behind it. The attack chain demonstrates a strategic shift toward fileless execution, abuse of legitimate Windows features, complex command-and-control concealment, and highly resilient persistence mechanisms that make remediation exceptionally difficult.
The findings suggest that Gamaredon has moved beyond traditional malware deployment into a layered ecosystem where every component can independently receive instructions, download additional payloads, and maintain communication with operators. The result is a cyber weapon that behaves more like a living organism than conventional malware.
Sekoia’s Hunt Uncovers a New Generation of Gamaredon Malware
Sekoia’s Threat Detection & Research team first identified suspicious activity after deploying a new YARA hunting rule in late December 2025. Within weeks, multiple detections pointed researchers toward an unfamiliar infection chain.
The investigation revealed an upgraded version of
Researchers have now standardized the naming convention for the group’s malware families under a unified “Gamma” taxonomy:
GammaPhish – Initial Access
GammaLoad – Payload Staging
GammaWorm – Propagation
GammaSteel – Information Theft
GammaWipe – Destructive Operations
While the naming structure is new, the strategic objective remains unchanged. Gamaredon continues to focus heavily on intelligence gathering and long-term access within Ukrainian targets.
The Attack Begins with a Deceptively Simple XHTML File
The infection process starts with what appears to be an ordinary XHTML document delivered through spear-phishing campaigns.
At first glance, the file appears harmless. Yet opening it immediately triggers a hidden request to a Supabase endpoint using a tiny 1×1 tracking pixel.
This serves a critical purpose. It silently informs the attacker that the victim has opened the lure document.
The technique is remarkably old, dating back several years. Yet its continued effectiveness highlights a recurring reality in cybersecurity: attackers often succeed not through groundbreaking innovation, but by consistently exploiting human behavior.
Once victim engagement is confirmed, the XHTML file initiates an HTML smuggling process that downloads a malicious RAR archive.
Exploiting WinRAR Through CVE-2025-8088
The downloaded archive abuses CVE-2025-8088, a critical path traversal vulnerability affecting WinRAR before version 7.13.
Victims believe they are extracting a harmless PDF document. Instead, the archive secretly contains a hidden HTA file alongside the visible decoy.
Through path traversal manipulation, the HTA file is automatically extracted into the Windows Startup folder.
The next time the user logs in, Windows executes the malicious file without requiring any further interaction.
The same vulnerability was reportedly exploited by several Russian-linked threat actors, including Sandworm and Turla, demonstrating how quickly valuable exploits circulate among advanced cyber operators.
GammaLoad Uses Legitimate Windows Tools to Blend In
Once executed, the malicious HTA launches
To reduce suspicion, the command includes references resembling BBC URLs, making network traffic appear less suspicious during casual inspection.
This stage downloads GammaLoad, the
Although researchers were unable to retrieve GammaLoad directly due to inactive command-and-control infrastructure during analysis, forensic evidence from compromised systems provided substantial insight into its functionality.
GammaLoad operates through multiple VBScript stages designed to:
Fingerprint infected systems
Modify registry-based network configurations
Resolve command-and-control infrastructure
Download and execute additional payloads
Maintain communication with operators
The staged design allows Gamaredon operators to modify campaigns dynamically without rebuilding the entire infection chain.
GammaWorm Becomes the Core of the Operation
The most technically sophisticated component identified by Sekoia is GammaWorm.
After deobfuscation, researchers discovered a massive VBScript payload exceeding 20,000 lines of code.
Most of those lines serve no operational purpose. Instead, they exist solely to overwhelm analysts, complicate reverse engineering efforts, and increase investigation time.
This technique reflects a growing trend among advanced threat actors: exhausting defenders through complexity rather than relying solely on technical exploits.
Alternate Data Streams Enable Near-Invisible Malware Storage
One of
ADS is a legitimate Windows feature that allows additional data to be attached to files and folders without appearing in standard directory listings.
Traditional commands such as:
dir
cannot easily reveal these hidden streams.
GammaWorm stores core modules inside ADS locations, dramatically reducing visibility for administrators and security tools.
Because the malware avoids traditional file creation, many endpoint monitoring solutions may struggle to identify malicious artifacts during routine inspections.
Persistence Designed to Survive Cleanup Attempts
Persistence is where Gamaredon demonstrates extraordinary resilience.
GammaWorm creates three scheduled tasks disguised as legitimate Windows services:
DiskDiagnosticDataCollector
SilentCleanup
SmartRetry
Each task periodically executes hidden malware modules every few minutes.
Additionally, the malware abuses the RunOnce registry mechanism.
Normally, RunOnce entries execute once and disappear automatically. Gamaredon cleverly recreates the registry key before deletion occurs, effectively transforming a one-time execution feature into a permanent persistence mechanism.
This redundancy ensures that even if defenders remove one persistence layer, others remain active.
USB Drives Become Infection Carriers
GammaWorm actively targets removable storage devices and network shares.
The malware hides legitimate folders by assigning Hidden and System attributes.
It then replaces them with malicious shortcut files that mimic the original folder names and icons.
When victims click the shortcut, Windows opens the legitimate folder, creating the illusion that nothing unusual happened.
Simultaneously, the malware executes hidden worm components stored elsewhere on the device.
The campaign includes both mundane filenames and emotionally provocative lures designed to maximize click rates.
This demonstrates that even state-sponsored cyber operators continue to rely heavily on social engineering.
Telegram Becomes a Command-and-Control Delivery System
Perhaps the most creative aspect of the campaign is its command-and-control resolution process.
Instead of directly contacting attacker infrastructure, GammaWorm retrieves information from public Telegram channels.
Using curl commands, the malware downloads webpage content and extracts obfuscated IP addresses.
The chain then routes through multiple intermediary services including:
Telegram
Telegra.ph
Teletype
Graph.org
Cloudflare Workers
Only after traversing these platforms does the malware reach attacker-controlled infrastructure.
This layered approach creates significant challenges for defenders attempting to identify or block malicious communications.
Data Hidden Inside HTTP Headers
Another unusual technique involves data transmission.
Rather than sending information through conventional HTTP request bodies, GammaWorm embeds victim fingerprints inside HTTP headers.
Specifically, information is hidden within User-Agent strings.
This approach helps malware blend into legitimate web traffic while bypassing certain monitoring systems focused primarily on payload content.
Even more interesting is the
A normal HTTP 404 error usually indicates missing content.
Gamaredon repurposes 404 responses as configuration update signals, effectively turning standard web behavior into a covert communication channel.
A Malware Architecture Built for Long-Term Survival
According to Sekoia researchers, the attack chain represents a major advancement over previously documented Gamaredon operations.
Every stage possesses independent capabilities for downloading and executing remote code.
This means defenders may remove one component only to discover another component has already restored functionality.
The architecture resembles nested Russian matryoshka dolls, with each layer containing another operational layer underneath.
Such design significantly increases the cost and complexity of incident response efforts.
For organizations affected by this campaign, traditional cleanup procedures may no longer be sufficient.
Researchers recommend complete system rebuilding and reinstallation as the safest remediation strategy.
What Undercode Say:
Gamaredon’s latest operation highlights an important reality often overlooked in cybersecurity discussions.
The most dangerous threat actors are not always those with the newest exploits.
They are often those who consistently improve proven techniques.
What stands out most is the strategic maturity of this campaign.
Gamaredon did not simply deploy new malware.
It built an ecosystem.
Every component has a purpose.
Every layer supports another.
Every stage can independently recover from disruption.
The use of ADS storage demonstrates a strong understanding of Windows internals.
Many organizations still focus heavily on executable detection.
Gamaredon instead hides operational components where administrators rarely look.
The campaign also reveals how threat actors increasingly abuse trusted internet platforms.
Telegram becomes infrastructure.
Cloudflare becomes infrastructure.
Graph.org becomes infrastructure.
Traditional security models struggle when malicious traffic flows through services widely used by legitimate users.
The continued reliance on VBScript is particularly interesting.
Many security professionals consider VBScript outdated.
Gamaredon appears to view it as ideal.
Legacy technologies often receive less scrutiny than modern attack vectors.
The infection chain also demonstrates operational patience.
Tracking pixels confirm victim interaction before deploying additional stages.
This minimizes exposure and reduces unnecessary infrastructure use.
Another critical observation is the
Most malware seeks persistence.
Gamaredon seeks persistence redundancy.
Three scheduled tasks.
Registry manipulation.
ADS storage.
Multiple payload stages.
Independent code execution.
Each mechanism compensates for the potential failure of another.
The command-and-control design deserves special attention.
Historically, security teams blocked IP addresses.
Then domains.
Now attackers increasingly use dynamic resolution chains spanning multiple platforms.
This dramatically complicates attribution and takedown efforts.
The use of HTTP headers for data transmission further demonstrates an understanding of modern detection methodologies.
Security products inspect payloads extensively.
Headers often receive less scrutiny.
Gamaredon continues exploiting these visibility gaps.
The
Fileless attacks significantly reduce forensic evidence.
Investigators depend on artifacts.
Artifacts become scarce when malware operates primarily in memory.
The campaign shows signs of long-term strategic investment.
This was not an overnight development.
The architecture likely evolved through years of operational feedback.
Each improvement appears designed to address weaknesses discovered during previous campaigns.
Organizations defending against nation-state actors must recognize a critical lesson.
Detection alone is no longer enough.
Visibility, threat hunting, behavioral analytics, memory monitoring, and rapid containment are becoming equally important.
Gamaredon’s evolution suggests future campaigns may become even more decentralized and adaptive.
The threat actor appears committed to survivability above all else.
That mindset makes them exceptionally difficult to remove once access has been established.
Deep Analysis
Investigating Alternate Data Streams
Get-Item -Path "C:\Users\Public" -Stream
dir /r
Enumerating Scheduled Tasks
Get-ScheduledTask | Select TaskName,State
schtasks /query /fo LIST /v
Inspecting RunOnce Registry Keys
Get-ItemProperty "HKCU:\Software\Microsoft\Windows\CurrentVersion\RunOnce"
reg query HKCU\Software\Microsoft\Windows\CurrentVersion\RunOnce
Monitoring mshta Activity
Get-Process mshta
tasklist | findstr mshta
Identifying Suspicious Network Connections
Get-NetTCPConnection
netstat -ano
Hunting for Hidden VBScript Execution
Get-WinEvent -LogName Security
wevtutil qe Security
Memory-Based Threat Detection
volatility -f memory.raw windows.pslist
volatility -f memory.raw windows.netscan
Endpoint Investigation
Get-ChildItem -Recurse -Force
wmic startup get caption,command
✅ Sekoia researchers did identify a new Gamaredon infection chain using YARA-based hunting techniques and documented a significantly more modular architecture.
✅ The campaign leveraged CVE-2025-8088 in WinRAR to facilitate hidden file extraction and persistence mechanisms through Windows Startup folders.
✅ The malware extensively abused NTFS Alternate Data Streams, scheduled tasks, registry persistence, and Telegram-based infrastructure, representing a measurable technical advancement compared to earlier publicly documented Gamaredon campaigns.
Prediction
(+1) Gamaredon will likely continue expanding its fileless malware ecosystem, introducing additional modules that operate entirely in memory to further reduce forensic visibility.
(+1) Security vendors are expected to increase detection coverage around Alternate Data Streams, VBScript execution chains, and Telegram-based command-and-control infrastructure as awareness of these techniques grows.
(+1) Governments and critical infrastructure operators will accelerate investments in behavioral threat hunting platforms capable of identifying stealthy persistence mechanisms rather than relying solely on signature-based detection.
(-1) Organizations running outdated WinRAR versions and legacy Windows environments will remain attractive targets, leading to additional compromise campaigns leveraging similar archive-based exploitation techniques.
(-1) Traditional antivirus products that prioritize file scanning over behavioral monitoring may experience declining effectiveness against future Gamaredon operations.
(-1) Incident response costs are likely to increase as defenders face malware architectures designed specifically to survive partial remediation and rapidly re-establish control after cleanup attempts.
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References:
Reported By: securityaffairs.com
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