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 the MITRE ATT&CK framework:

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_DLLHIJACKER {
    meta:
        description = "Detects Dllhijacker (ransomware)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "dllhijacker" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Dllhijacker Activity
id: de6b0004eb1c2bd75db206a7e7705aa5
status: experimental
description: Detects generic indicators of the dllhijacker malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*dllhijacker*"
    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. 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)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Ubibila
• Idsohtu
• Blueeagle
• Wirzemro
• Lenwadu

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/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.