Analysis of APT-C-53 (Gamaredon) Attack on Ukrainian Government Agencies

SUMMARY :

APT-C-53, also known as Gamaredon, is a Russian state-sponsored threat group active since 2013, targeting Ukrainian government and military entities. The group has upgraded its attack techniques, focusing on dynamic cloud-based C2 infrastructure and targeted delivery of cloud storage tools. In 2025, they conducted high-density intelligence theft activities against Ukrainian government agencies. The attack chain involves dynamic changes in infrastructure, abuse of Microsoft Dev Tunnels, and sophisticated data exfiltration techniques. The group employs white-listed domain camouflage, domain shadowing, and weaponization of cloud tunnel services to evade detection. Their data theft process includes registry-based persistence, multi-stage payload delivery via Cloudflare Workers, and exfiltration through legitimate cloud tools like Dropbox.

OPENCTI LABELS :

apt,powershell,russia,ukraine,dropbox,vbscript,cyberespionage,cloudflareworkers,devtunnels


AI COMMENTARY :

1. Introduction: In early 2025, cybersecurity analysts uncovered a sophisticated campaign orchestrated by APT-C-53, also known as Gamaredon, targeting Ukrainian government agencies. This Russian state-sponsored threat group has been active since 2013, employing a diverse arsenal that includes PowerShell scripts, VBScripts, and advanced cloud-based tactics. The recent attack wave demonstrated an upgraded approach to cyberespionage, leveraging Microsoft Dev Tunnels, dynamic domain shadowing, and weaponized cloud services to infiltrate high-value targets in Ukraine’s public sector.

2. Historical Context and Threat Profile: APT-C-53 emerged in the wake of heightened geopolitical tensions, focusing its operations on military and government entities within Ukraine. Over the years, analysts have observed a consistent evolution in the group’s sophistication, moving from rudimentary phishing lures to highly targeted spear-phishing campaigns. The persistent nature of this Russian-aligned actor reflects its strategic objective: gathering political and military intelligence to support broader state interests. By 2025, Gamaredon had refined its tactics to evade traditional security controls, earning a reputation for resilience and adaptability in cyberespionage.

3. Attack Chain and Techniques: The core of the Gamaredon operation rests on a multi-stage attack chain. Initial compromise often begins with a spear-phishing message containing malicious attachments or links. Upon execution, a PowerShell dropper establishes registry-based persistence and initiates communication with a dynamic command-and-control (C2) server. The group’s use of VBScripts within weaponized documents adds an additional layer of stealth, delaying detection by conventional antivirus solutions. Throughout the campaign, the operators continuously rotate IP addresses and domains, rendering static blocklists ineffective.

4. Infrastructure Dynamics and Evasion: Central to the group’s success is its dynamic cloud-based C2 infrastructure. Gamaredon leverages Cloudflare Workers to host multi-stage payloads, enabling direct retrieval of executables without exposing primary servers. This approach, combined with abuse of Microsoft Dev Tunnels, allows attackers to proxy traffic through legitimate Microsoft cloud endpoints. The group also employs domain shadowing and white-listed domain camouflage, registering subdomains under trusted domains to bypass network filters. Such tactics complicate attribution efforts and extend the lifespan of malicious infrastructure.

5. Exfiltration Phase and Tools: Once established, APT-C-53 operators focus on high-density intelligence theft. Files of interest are compressed and transferred through legitimate cloud storage services like Dropbox, thereby blending malicious traffic with benign user behavior. The final payload stage often includes a lightweight VBScript that automates the upload of reconnaissance data to the attacker-controlled Dropbox account. By harnessing trusted platforms for exfiltration, Gamaredon reduces the likelihood of triggering data loss prevention systems and network monitoring alerts.

6. Mitigation and Conclusion: Defenders facing the APT-C-53 threat must adopt a layered security approach that combines dynamic threat intelligence, heuristic analysis, and strict application control policies. Monitoring for anomalous use of Dev Tunnels and cloudflareworkers endpoints, enforcing multifactor authentication for cloud services, and maintaining up-to-date PowerShell logging can significantly reduce exposure. As Gamaredon continues to refine its cyberespionage toolkit, organizations in Ukraine and beyond must remain vigilant, sharing intelligence on emerging tactics to collectively thwart this adaptive adversary.


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Analysis of APT-C-53 (Gamaredon) Attack on Ukrainian Government Agencies