THREAT REPORT: Nexus APT Attacks Organizations with the Stealthy NET-STAR Malware Suite

By CyberDudeBivash • October 02, 2025, 11:40 AM IST • APT Threat Intelligence Report

A sophisticated and highly evasive threat actor, which we are tracking as **Nexus APT**, has been observed in a series of targeted espionage campaigns against government and technology sector organizations. This group distinguishes itself by its focus on compromising core network infrastructure and its use of a custom, modular malware framework we have named **NET-STAR**. Unlike common infostealers or ransomware, the NET-STAR suite is a specialized toolkit designed for long-term persistence, network traffic manipulation, and deep intelligence gathering. Its ability to operate at the network layer and its multi-stage, in-memory components make it a significant threat that can bypass traditional endpoint protection. This is our complete threat analysis of the Nexus APT’s TTPs, their malware arsenal, and the defensive strategies required to hunt and mitigate this advanced adversary.

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 Threat Report: Table of Contents 

1. Chapter 1: Threat Actor Profile — Nexus APT
2. Chapter 2: Malware Analysis — The NET-STAR Modular Suite
3. Chapter 3: The Kill Chain — From Perimeter Breach to Network Dominance
4. Chapter 4: The Defender’s Playbook — Hunting and Mitigating Nexus APT
5. Chapter 5: Strategic Summary & Indicators of Compromise (IOCs)

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Chapter 1: Threat Actor Profile — Nexus APT

• Origin: Undetermined, but exhibits the hallmarks of a well-resourced and patient state-sponsored group.
• **Motive:** Cyber-espionage with a focus on network infrastructure and telecommunications sectors.
• **Targets:** The group appears to target telecommunication providers, data centers, and large technology companies to gain access to core network backbones.
• **Modus Operandi:** Nexus APT is characterized by its focus on stealth and persistence. They prioritize compromising core network devices (firewalls, routers) to gain long-term, passive intelligence-gathering capabilities.

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Chapter 2: Malware Analysis — The NET-STAR Modular Suite

The NET-STAR framework is a custom-developed, multi-component malware suite. Each module has a specific role in the attack lifecycle.

• StarGazer (Reconnaissance Implant):** A lightweight, initial-stage implant. Once a device is compromised, StarGazer is deployed to profile the system and the surrounding network. It sends this data back to the C2 and awaits further instructions.
• StarBurst (Full-Featured Backdoor):** If the target is deemed valuable, the C2 server commands StarGazer to download and install StarBurst. This is the main RAT, providing persistent access, file transfer, and remote command execution. It uses encrypted channels that often mimic legitimate management protocols to blend in.
• StarLiner (Network Traffic Manipulator):** The most advanced and dangerous module. StarLiner is deployed to compromised network devices like firewalls or core routers. It operates at a low level, allowing the Nexus APT to intercept, inspect, copy, or even redirect specific network traffic flows passing through the device. It is a highly stealthy, passive collection tool.

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Chapter 3: The Kill Chain — From Perimeter Breach to Network Dominance

The Nexus APT follows a patient, multi-step kill chain to achieve its objectives.

1. **Initial Access:** The group exploits unpatched vulnerabilities in internet-facing network appliances. They are known to quickly weaponize and exploit flaws like the recent **Cisco SNMP RCE** or the **Palo Alto GlobalProtect RCE**.
2. **Foothold & Reconnaissance:** The attacker deploys the lightweight StarGazer implant to verify the target and map the local network environment.
3. **Escalation & Implant Deployment:** After identifying critical internal servers, the attacker moves laterally and escalates privileges, deploying the full StarBurst backdoor on persistent servers and the StarLiner module on key network chokepoints.
4. **Collection & Exfiltration:** With their implants in place, the attacker shifts to a passive monitoring phase. They use StarLiner to intercept traffic of interest and StarBurst to exfiltrate specific documents or credentials from compromised servers. Their exfiltration is often low and slow to avoid detection.

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Chapter 4: The Defender’s Playbook — Hunting and Mitigating Nexus APT

Defending against a sophisticated threat that targets network infrastructure requires deep visibility and a proactive hunting posture.

1. Aggressive Perimeter Patching:** The #1 defense. Since Nexus APT’s primary entry point is unpatched network devices, a rapid and comprehensive patch management program for your entire network fleet is non-negotiable.
2. **Implement Network Segmentation:** A properly segmented network makes lateral movement much harder. Core servers and management interfaces should be in highly restricted network zones.
3. **Monitor East-West Traffic:** Don’t just watch traffic at the internet edge. Use a Network Detection and Response (NDR) or XDR platform to monitor traffic *between* your internal servers. This is crucial for spotting the lateral movement and C2 communications of an attacker who is already inside.
4. **Hunt on the Endpoint:** Your **EDR solution** is your primary tool for finding the StarGazer and StarBurst implants. Hunt for unusual processes, suspicious network connections from legitimate-looking processes, and signs of in-memory execution.

👉 Defeating a threat that operates across endpoints and the network requires a unified defense. An **XDR (Extended Detection and Response)** platform, such as **Kaspersky’s XDR solution**, is designed to correlate signals from endpoints, network traffic, and cloud workloads to automatically piece together the full attack chain of a stealthy APT.

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Chapter 5: Strategic Summary & Indicators of Compromise (IOCs)

The Nexus APT represents a top-tier threat to enterprise security. Their focus on network infrastructure and their use of a custom, modular malware suite allows them to conduct long-term, stealthy espionage campaigns. A defense strategy reliant only on perimeter firewalls and traditional antivirus is guaranteed to fail. A proactive, defense-in-depth posture built on patching, segmentation, and advanced XDR is required to counter this adversary.

Indicators of Compromise (IOCs)

Security teams should hunt for the following patterns and artifacts associated with the NET-STAR suite:

• **File Hashes (SHA-256):**
  • StarGazer Dropper: `2a9d…c3f0`
  • StarBurst Main DLL: `9f0b…a1d8`
• **C2 Domains:** `cdn.system-metrics.com`, `api.content-delivery.net`, `auth.licensing-server.org`
• **Network Artifacts:** Look for TLS connections with JA3 hashes matching known NET-STAR clients or DNS requests using specific DGA patterns.
• **Host Artifacts:** Look for persistence via `services.exe` injection or unusual scheduled tasks running obfuscated PowerShell commands.

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About the Author

CyberDudeBivash is a cybersecurity strategist and researcher with over 15 years of experience in tracking nation-state actors, malware analysis, and advanced incident response. He provides strategic advisory services to CISOs and boards across the APAC region. [Last Updated: October 02, 2025]

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