Mosucker

Overview

Backdoor:Win32/Mosucker is a stealthy remote access trojan (RAT) or backdoor designed to provide threat actors with persistent, undetected, and interactive access to a compromised network. It allows attackers to exfiltrate data, monitor user activity, and deploy additional malware payloads on demand.

Understanding Mosucker
To a victim, a Mosucker infection is completely silent. For a SOC analyst, Mosucker represents a critical breach involving 'hands-on-keyboard' access. Once deployed, the attacker can seamlessly traverse the network, steal high-value credentials, exfiltrate sensitive data, and deploy further destructive payloads, all while appearing as legitimate background system activity.

Execution, Evasion, and Interactive Control
Mosucker is typically deployed by initial access brokers, dropped via exploit kits, or executed through macro-enabled spear-phishing documents (`T1566.001`). Upon execution, it heavily relies on Process Injection or Process Hollowing (`T1055`), often unpacking its payload directly into the memory space of a legitimate process like `svchost.exe`. It establishes persistence via hidden Registry keys or Services (`T1543.003`). The backdoor provides a massive suite of capabilities: live keylogging, password recovery, remote command execution (`T1059`), and the ability to seamlessly download and execute secondary malware (`T1105`). Mosucker often uses customized, encrypted protocols for its C2 communications to evade network IDS (`T1071.001`).

Indicators of Compromise & Impact
The impact is total endpoint compromise and the high probability of lateral movement across the enterprise. Host-based IoCs require careful EDR monitoring: look for legitimate system processes initiating outbound, encrypted network connections to unknown IP addresses, or anomalous child processes spawning from `explorer.exe`. Memory analysis is almost always required to locate the unencrypted Mosucker payload residing in hollowed memory segments.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1059: Restrict execution of scripting languages such as PowerShell, VBScript, or Python to authorized administrators. Enforce Script Block Logging.
• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_MOSUCKER {
    meta:
        description = "Detects Mosucker (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "mosucker" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Mosucker Activity
id: 170b0d3ab08c94d3f65736c111b1eae7
status: experimental
description: Detects generic indicators of the mosucker malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*mosucker*"
    condition: selection
level: medium

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Immediately isolate the infected endpoint from the network to sever the attacker's interactive control session and halt lateral movement.
2. Assume all credentials typed on the machine or stored locally have been stolen, and mandate immediate enterprise-wide password resets for the affected user.
3. Perform a deep memory forensics analysis to extract the Mosucker payload and determine its exact C2 infrastructure for network-wide blocking.
4. Do a thorough hunt across the environment for lateral movement, as the attacker likely used the backdoor to compromise file shares or domain controllers.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not assume the attack is thwarted if an AV engine quarantines a dropper; the Mosucker backdoor itself may already be running resident in memory.
2. Avoid rebooting the machine before capturing a memory image, as the decrypted payload and critical forensic evidence will be lost.

References & External Analysis

• Search "mosucker" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Polypatch
• Tsklnk
• Rz0Auircb0Di
• Inexsmar
• Ursnifdropper

Machine-readable

Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/api/mosucker.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.