Dllhijacker

Overview

Trojan:Win32/Dllhijacker is a generic heuristic detection used by antivirus engines to classify malware that specifically relies on **DLL Search Order Hijacking** (`T1574.001`) to execute its payload. This is a highly advanced evasion and privilege escalation technique where malware replaces a legitimate, expected Dynamic Link Library (DLL) with a malicious fake, tricking a trusted system process into loading the malware into its own memory space.

Understanding DLL Hijacking
To an end-user, this attack is completely invisible. For a security analyst, a Dllhijacker detection indicates a sophisticated adversary attempting to bypass application whitelisting (like AppLocker) and evade EDR by hiding within the context of a trusted Microsoft process. APT groups and advanced ransomware families frequently utilize this technique for stealthy persistence.

Execution and Hijacking Mechanics
When a Windows application starts, it often doesn't specify the exact, absolute path to the DLLs it needs. Instead, it relies on the Windows DLL Search Order (checking the application directory first, then `System32`, then the PATH). The malware exploits this by dropping a malicious DLL, named identically to a legitimate missing DLL, into a directory higher up in the search order (often the application's own directory) (`T1574.001`). When the legitimate executable runs (`T1204.002`), it inadvertently loads the malicious DLL (`T1055.001`). The malicious DLL executes its payload (often a beacon or downloader), and then uses API forwarding to seamlessly pass the legitimate function calls back to the real DLL, ensuring the parent application doesn't crash and the user notices nothing.

Indicators of Compromise & Impact
The impact is stealthy, persistent execution of malware disguised as trusted processes. The primary IoC is EDR alerts detecting unsigned DLLs being loaded by signed, native Windows executables (e.g., `calc.exe` or `msteams.exe` loading a malicious `version.dll` from the `%AppData%` directory). Threat hunters should look for newly created `.dll` files in unexpected directories alongside legitimate executables.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

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_DLLHIJACKER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Dllhijacker"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "dllhijacker" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Dllhijacker (Ransomware) Execution & Triage
id: 66bc7b13-57a5-5745-8d80-82107c807d26
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Dllhijacker 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/dllhijacker
- 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.t1204_002
- attack.t1574_001
- attack.t1547
- attack.t1055_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_DLLHIJACKER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Dllhijacker 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 = "dllhijacker" 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 endpoint. Because the malware is running inside a legitimate process, simply killing the process may crash the system or the application will just restart and re-load the malicious DLL.
2. Utilize EDR to identify the specific signed executable that was exploited and the exact path of the malicious, unsigned DLL it loaded.
3. Delete the malicious DLL from the file system. Ensure the legitimate application is reinstalled or repaired if necessary.
4. Audit the system for any secondary payloads downloaded by the hijacked process.

What to Avoid

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

1. Do not blindly trust an executable just because it is digitally signed by Microsoft; if it is vulnerable to DLL hijacking, it can be weaponized.
2. Avoid assuming standard AV will catch this; if the malicious DLL is well-obfuscated, the AV will only see a trusted process running.

References & External Analysis

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

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Clearsearch
• Dlzp
• Pres
• Creprote
• Grandcrap
• Naco
• Malwares
• Kradword

Machine-readable

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