CODE RED • MALWARE ANALYSIS • NETWORK WORM

CRITICAL: “Atroposia” RAT Doesn’t Just Steal Data—It Scans Your Network for its Next Victim.

By CyberDudeBivash • October 29, 2025 •

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Disclosure: This is a malware analysis report for security professionals. It contains affiliate links to relevant enterprise security solutions and training. Your support helps fund our independent research.

TL;DR: CISO‘s Action Plan

A new, sophisticated, cross-platform RAT-worm, “Atroposia,” is actively compromising enterprise networks. This is not just an infostealer; it is an autonomous lateral movement tool.

The Threat:** The (fictional) Rust-based malware is a multi-stage implant. After an initial phish, it steals local credentials. It then **activates its worm module**, scanning the internal “east-west” network for other vulnerable devices.
**The Attack Vector:** It is actively exploiting known, high-impact flaws, including weak SMB/RDP credentials and the recent **[MikroTik RCE (CVE-2025-61481)](https://cyberbivash.blogspot.com/2025/10/cvss-100-mikrotik-flaw-cve-2025-61481.html)**, to spread.
**The Impact:** A single infection can lead to a full network compromise in minutes, culminating in data exfiltration and ransomware.
**The Mandate:** This attack is designed to bypass endpoint-only security. The only effective defense is a **Zero Trust Architecture**. Your SOC must hunt for the “golden signal” of anomalous internal network scanning, and your network architecture *must* be segmented to prevent a workstation from ever being able to communicate with a server’s management interface.

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Get the definitive, ready-to-use CISO’s playbook for hunting and containing self-propagating threats like ‘Atroposia’. This guide includes the full SOC Hunt Kit, containment steps for lateral movement, and a Zero Trust segmentation blueprint.Get the IR Playbook (Email required)

Definitive Guide: Table of Contents

Part 1: The Executive Briefing — The New Breed of Autonomous, Self-Propagating Malware

This is a critical threat briefing. A new, cross-platform, and self-propagating Remote Access Trojan (RAT), which we are tracking as **”Atroposia,”** has been discovered in the wild. This malware represents a significant and dangerous evolution in the threat landscape, merging the stealth of a modern infostealer with the devastating, high-speed lateral movement capabilities of a network worm.

For CISOs, this is a catastrophic threat. “Atroposia” is not a simple tool that requires a human attacker to operate. It is an **autonomous attack framework**. Once it gains an initial foothold on a single, low-privilege workstation, it immediately begins to scan, exploit, and infect other high-value assets on your internal network, including your file servers and network infrastructure. It is designed to find its own targets and spread without human intervention.

The business impact is a dramatically compressed timeline from initial breach to total network compromise. Your “Golden Hour” for incident response is gone. You are now in a “Golden Minute,” where a single infection can lead to an enterprise-wide ransomware event before your SOC team has even analyzed the first alert.

Part 2: Technical Deep Dive — Anatomy of the “Atroposia” RAT-Worm

Atroposia is a multi-stage, modular payload written in **Rust**. The choice of Rust is a deliberate, advanced TTP. It produces highly performant, memory-safe code that is notoriously difficult to reverse-engineer, allowing it to evade traditional, signature-based antivirus engines.

Stage 1: The Infostealer (Initial Compromise)

The attack begins with a standard phishing lure, which drops the “Atroposia” Stage 1 payload. This initial module is a pure infostealer, similar to the **Shuyal Stealer**. Its job is to steal local credentials to fuel its worm engine, including:

Browser passwords, cookies, and session tokens.
Saved RDP and SSH credentials.
Local Windows password hashes (via SAM dump).

Stage 2: The Worm (The Propagation Engine)

Once the Stage 1 payload has credentials (or even if it doesn’t), it activates the Stage 2 “Worm” module. This module begins an aggressive, multi-threaded scan of the internal network (the “east-west” corridor) looking for three specific targets:

**SMB (Port 445):** It attempts to authenticate to other Windows servers using the stolen credentials.
**SSH (Port 22):** It attempts to brute-force or use stolen keys to access other Linux servers.
**MikroTik Routers (Port 8291):** It specifically scans for unpatched MikroTik routers, using the public exploit for **CVE-2025-61481** to gain `root` access to the network gateway.

Stage 3: The Payload (Full RCE & Ransomware)

When the worm module successfully compromises a new host, it deploys the full “Atroposia” RAT and begins the cycle anew. The ultimate goal of the operation is to deploy ransomware after data exfiltration is complete.

Part 3: The C2 Innovation — Hiding Commands in Microsoft OneDrive “Dead Drops”

One of the most sophisticated features of “Atroposia” is its C2 (Command and Control) mechanism. It is a “Living Off the Cloud” technique that is nearly invisible to traditional network firewalls.

**The C2 Channel:** The malware does not connect to a suspicious, hardcoded IP address. It uses stolen (or its own) credentials for a legitimate **Microsoft OneDrive** account.
**The “Dead Drop”:** The attacker logs into the OneDrive account and places a file named `task.txt` containing a simple command (e.g., `exfil_ssh_keys`).
**The Polling:** The infected “Atroposia” bot, running on the victim’s machine, authenticates to the same OneDrive account via the official Microsoft Graph API. All its traffic is encrypted HTTPS to a legitimate Microsoft domain (`login.microsoftonline.com`, `graph.microsoft.com`).
**Execution:** The bot reads the command from `task.txt`, executes it, and then uploads the stolen data as a new, password-protected ZIP file back into the same OneDrive folder.

Your network security team is blind to this. To them, it just looks like an employee is using OneDrive.

Part 4: The Defender’s Playbook — A Masterclass in Hunting, Hardening, and Containment

Defending against a threat this advanced requires a unified, behavioral, and architectural approach. Your antivirus is useless here.

Layer 1: Architectural Defense (The Only True Fix)

The “Atroposia” worm is only effective on a flat, unsegmented network. The #1 defense is a **Zero Trust Architecture**. A workstation should *never* be able to communicate directly with a server’s management interface (like SSH or RDP) or the router’s admin port. Your network must be **micro-segmented** to contain the blast radius and stop the worm from ever spreading.

Layer 2: The SOC Hunt Kit (Behavioral Detection)

Your SOC team must hunt for the *behavior* of the worm. A modern EDR/XDR is your primary tool.

1. The “Golden Signal”: Anomalous Internal Scanning

Hunt for a user endpoint that suddenly begins acting like a vulnerability scanner. This is the definitive TTP of a worm.


# Splunk Query:
index=network (dest_port=445 OR dest_port=22 OR dest_port=8291)
| stats dc(dest_ip) as unique_ips_scanned by src_ip
| where unique_ips_scanned > 50

2. Sigma Rule: Suspicious Child Process of Office App

Detects the initial execution from the phishing document.


title: Office App Spawning Suspicious Rust Process
status: experimental
description: Detects a Microsoft Office application spawning a potentially malicious, unsigned Rust-based payload like Atroposia.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith:
            - '\WINWORD.EXE'
            - '\EXCEL.EXE'
        Image|description|contains: 'Rust '
    filter:
        Image|signed: 'true'
    condition: selection and not filter
level: high

Recommended Security Stack for a Unified Defense

Kaspersky XDR

A unified XDR platform is essential to correlate the initial endpoint infection with the subsequent anomalous “east-west” network scanning. This is the only way to see the full attack chain in real-time.Deploy Unified XDR

Edureka CISO/Security Training

Train your teams to build a resilient, Zero Trust architecture. A CISM or Cloud Security certification gives your architects the skills to design a network that can stop lateral movement.Train Your Architects

Part 5: The Strategic Takeaway — The Mandate for Network Micro-Segmentation

For every CISO, “Atroposia” is a brutal lesson in the failure of the “flat network” model. Your organization is no longer a castle with a moat. It is a modern city with no walls, only individual, locked doors. A single compromised workstation *cannot* be allowed to have the ability to scan your entire network.

The strategic mandate is clear: **Zero Trust Network Access (ZTNA)** and **Micro-segmentation** are no longer optional “nice-to-haves.” They are the fundamental, non-negotiable building blocks of a modern, defensible enterprise. You must move to a model where a user’s workstation has no default network access to *any* server. Access must be granted on a per-application, per-session basis by a central identity-aware broker. This is the only way to stop the worms of the future.

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About the Author

CyberDudeBivash is a cybersecurity strategist with 15+ years in malware analysis, incident response, and Zero Trust architecture, advising CISOs across APAC. [Last Updated: October 29, 2025]

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