Dllhijack

Overview

Exploit:Win32/Dllhijack refers not to a specific malware family, but to a critical execution and defense evasion technique (`T1574.001` - DLL Search Order Hijacking). Antivirus engines use this detection when they observe a known good, legitimate application (like a signed Microsoft binary or a popular third-party tool) being manipulated to load a malicious Dynamic Link Library (DLL) instead of its intended, legitimate DLL.

Understanding DLL Hijacking (Defense Evasion)
To an end-user, the infection is entirely invisible. For a security team, a Dllhijack detection is a severe warning that an attacker is utilizing advanced 'Living off the Land' (LotL) techniques. Because the malicious code runs inside the memory space of a trusted, digitally signed process, it easily bypasses basic AV signatures, application whitelisting (AppLocker), and often blends in with normal EDR logs.

Execution and Evasion Mechanics
When a Windows application needs to load a DLL, it searches directories in a specific order (the directory the app was launched from, then System32, then the Windows folder, etc.). Attackers exploit this by dropping a malicious DLL (named identically to a required system DLL, e.g., `version.dll` or `cryptbase.dll`) into the same directory as the vulnerable application. When the legitimate application runs, it unknowingly loads the attacker's DLL first, executing the malicious payload (like Cobalt Strike or a ransomware encryptor).

Indicators of Compromise & Impact
The impact is total system compromise, achieved stealthily. Host-based IoCs include the presence of unsigned DLLs residing in directories where they do not belong (e.g., a system DLL sitting in `%AppData%` next to a copied legitimate executable). EDR solutions must analyze image load events to detect unsigned modules loading into signed processes. Process Explorer can be used to verify the digital signatures of all loaded modules for a suspected process.

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

Sigma Rule

title: Suspicious Dllhijack Activity
id: cf88e2dc4a10bd8c42902493cc1f882e
status: experimental
description: Detects generic indicators of the dllhijack malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*dllhijack*"
    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 immediately; if DLL hijacking is detected, the attacker has likely already achieved persistence or is moving laterally.
2. Identify the legitimate application that was abused and the malicious DLL that was loaded.
3. Analyze the malicious DLL in a sandbox to determine what payload it actually executed (e.g., C2 beaconing, encryption).
4. Implement strong folder permissions to prevent standard users from writing DLLs into application installation directories.

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 legitimate, signed application is the virus; deleting `explorer.exe` because it loaded a bad DLL will break the system.
2. Avoid relying solely on static file hashes for detection, as attackers frequently recompile the malicious DLLs.

References & External Analysis

• Search "dllhijack" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Smee
• Zard
• Xizfawwyz0Ab
• Lyrics
• Strictorcrtd

Machine-readable

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