Eskimo

Overview

Backdoor:Win32/Eskimo is a persistent Remote Access Trojan (RAT) designed to provide attackers with covert, interactive control over a compromised system. True to its name, Eskimo focuses heavily on stealth and espionage, allowing operators to exfiltrate sensitive documents, monitor user activity, and maintain a long-term presence within a network without triggering traditional alarms (`T1059`).

Understanding Eskimo (Covert Backdoor)
To an end-user, the infection is entirely invisible. For an incident response team, the presence of Eskimo indicates a targeted attack or an advanced persistent threat (APT) scenario, where the adversary is prioritizing intelligence gathering and lateral movement over immediate, noisy monetization (like ransomware).

Execution and Covert Mechanics
Eskimo is typically delivered via highly targeted spearphishing campaigns or dropped after initial exploitation of a vulnerable web service. Upon execution, it employs advanced evasion techniques, often utilizing API unhooking or direct syscalls to bypass EDR monitoring (`T1562.001`). It establishes persistence covertly, sometimes utilizing DLL Search Order Hijacking (`T1574.001`) or WMI event subscriptions (`T1546.003`) rather than noisy Registry Run keys. It communicates with its C2 server using customized, encrypted protocols, often blending in with normal HTTPS or DNS traffic (`T1071.001`) to evade network intrusion detection systems.

Indicators of Compromise & Impact
The primary impact is the severe loss of confidentiality and intellectual property theft. Host-based IoCs require deep forensics: EDR alerts for anomalous DLL loads, unusual WMI activity, or legitimate processes (like `svchost.exe`) making unexpected network connections. Network IoCs are subtle, often manifesting as regular, low-volume 'beaconing' traffic to unknown IP addresses or domains with recently registered, anomalous names.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official 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.

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

Tiered Detection Rules (Cisco CAIRN Model)

Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:

rule MALWARE_WIN_ESKIMO_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Eskimo"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "eskimo" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Eskimo (Ransomware) Execution & Triage
id: 281ae2cb-2a32-5656-8296-0d0962631e2c
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Eskimo malware family. Detects volume shadow copy deletion, boot status
  tampering, and recovery inhibition characteristic of modern ransomware operations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/eskimo
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.ransomware
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1574_001
- attack.t1005
- attack.t1059
- attack.t1071_001
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \vssadmin.exe
    - \wmic.exe
    - \wbadmin.exe
    - \bcdedit.exe
    CommandLine|contains:
    - delete shadows
    - shadowcopy delete
    - resize shadowstorage
    - recoveryenabled no
    - ignoreallfailures
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: critical

rule MALWARE_WIN_ESKIMO_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Eskimo tradecraft"
        tier = "T3 - Attribution Fingerprint"
        confidence = "High (Confirmed Family Signature)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        // Core family identifier & heuristic payload signatures
        $attrib_str = "eskimo" ascii wide nocase
        $pe_magic = "MZ" ascii
        $net_marker = "http" ascii nocase
    condition:
        uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}

Containment & Response Steps

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

1. Isolate the machine immediately to sever the attacker's interactive control and halt data exfiltration.
2. Assume all credentials present on the machine have been compromised and initiate an immediate, enterprise-wide password reset for the affected user.
3. Capture a full memory dump (RAM) before remediation to analyze the decrypted Eskimo configuration and identify its specific C2 infrastructure.
4. Hunt for the identified C2 IPs and domains across firewall logs to determine if the attacker successfully pivoted to other endpoints.

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 contained to a single machine; backdoors like Eskimo are primarily used as beachheads for lateral movement.
2. Avoid relying solely on automated AV removal, as the attacker likely established secondary, manual persistence mechanisms.

References & External Analysis

• Search "eskimo" on VirusTotal (External Analysis)
• Search "eskimo" on Any.Run (Sandbox Sandbox)
• Search "eskimo" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Kirts
• Safebreas
• Myransom
• Food
• Woripecs
• Avkiller
• Powzip
• Droma

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/eskimo.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.