Arcdoor

Overview

Backdoor:Win32/Arcdoor is a persistent, stealthy backdoor trojan designed to provide remote attackers with interactive, unauthorized access to a compromised endpoint. Once installed, it acts as a silent conduit, allowing threat actors to exfiltrate data, monitor user activity, and deploy further malicious modules at will.

Understanding Arcdoor
To an end-user, an Arcdoor infection is completely invisible; there are no pop-ups, ransom notes, or obvious system slowdowns. For a security analyst, a backdoor like Arcdoor represents a critical, ongoing breach of the network. It means an attacker has established a beachhead and can bypass perimeter security controls (like firewalls) by maintaining an outbound, reverse-shell connection to their Command and Control (C2) infrastructure.

Execution and Command Mechanics
Arcdoor is typically deployed as a secondary payload by an initial access broker, or via targeted spear-phishing (`T1566.001`). Upon execution, it establishes deep persistence, often by creating a hidden Windows Service (`T1543.003`) or modifying the `Winlogon` registry keys (`T1547.004`). It injects its core code into legitimate system processes like `svchost.exe` or `explorer.exe` (`T1055`) to camouflage its network activity. Arcdoor then initiates a covert beacon out to its C2 server, often using encrypted HTTP/HTTPS traffic or custom protocols over non-standard ports (`T1071.001`). Once a connection is established, the attacker has full remote control, capable of executing arbitrary shell commands (`T1059.003`), uploading/downloading files, and taking screenshots.

Indicators of Compromise & Impact
The impact is total loss of confidentiality and integrity on the compromised host, often leading to lateral movement across the enterprise. Host-based IoCs include EDR alerts for 'Suspicious Process Hollowing', anomalous outbound network connections originating from `svchost.exe` (especially to unknown IP addresses without corresponding DNS requests), and the creation of unexpected Windows Services.

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:

• T1059.003: Restrict execution of Windows Command Shell (cmd.exe) and block unauthorized batch scripts.
• 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_ARCDOOR {
    meta:
        description = "Detects Arcdoor (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "arcdoor" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Arcdoor Activity
id: 998a06b066af839695e44769dd2d3f74
status: experimental
description: Detects generic indicators of the arcdoor malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*arcdoor*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Isolate the endpoint from the network immediately to sever the active attacker connection and prevent lateral movement.
2. Analyze the memory of the running `svchost.exe` processes to identify the injected Arcdoor module and extract the C2 IP addresses/domains.
3. Block the identified C2 infrastructure at the corporate firewall and proxy, and hunt across the network for other endpoints communicating with those IPs.
4. Assume all credentials present on the infected machine have been compromised and initiate enterprise-wide password resets.

What to Avoid

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

1. Do not simply run a file-based AV scan and leave the machine online; backdoors often update themselves or deploy rootkits, requiring a full wipe and reimage.
2. Avoid investigating the endpoint on the live network, as the attacker may notice the investigation and deploy destructive wipers to cover their tracks.

References & External Analysis

• Search "arcdoor" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Alman
• Sasfis
• Nivdort
• Fakeplayer
• Kura

Machine-readable

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