Delfinject

Overview

Trojan:Win32/Delfinject is a heuristic detection identifying a specific, malicious behavior: a binary compiled in the Delphi programming language attempting to inject malicious code into the memory space of a legitimate Windows process. It is not a single malware family, but a technique commonly used by various Delphi-based threats, including banking trojans and RATs.

Understanding Delfinject
To an end-user, Delfinject is a standard antivirus warning. For incident responders, 'Delfinject' signifies that a payload has attempted a sophisticated evasion technique. Delphi (Object Pascal) was historically very popular among malware authors because the resulting binaries often had distinct structural differences from C++ malware, confusing older AV engines. The 'inject' portion of the name indicates the malware is attempting Process Hollowing or DLL Injection, ensuring the malicious code runs under the guise of a trusted application (like `explorer.exe` or `svchost.exe`).

Execution and Injection Mechanics
Delfinject-flagged files are often initial droppers or loaders distributed via malspam. Upon execution, the Delphi binary unpacks a secondary payload in memory (`T1027.002`). It then launches a legitimate Windows process in a suspended state (`CREATE_SUSPENDED`). It hollows out the memory of that legitimate process and writes its decrypted payload into that space (`T1055.012`). Finally, it resumes the thread. To the operating system and many task managers, it appears that a normal system file is running, but the executed code is entirely malicious.

Forensic Analysis & Impact
The impact depends entirely on the injected payload (which could be a banking trojan like Danabot or a RAT). EDR tools are vital here, as they monitor the behavioral anomaly of the process injection. Analysts must use memory forensics (like Volatility) to dump the memory of the injected process (`T1055`) to retrieve the true, unpacked payload for reverse engineering.

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.
• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.

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

Sigma Rule

title: Suspicious Delfinject Activity
id: 3b7083ed33b34272348417301b77d560
status: experimental
description: Detects generic indicators of the delfinject malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*delfinject*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Verify that the endpoint security solution successfully quarantined the Delphi executable and prevented the process injection.
2. If the injection succeeded, immediately isolate the endpoint from the network to prevent the hidden payload from establishing C2 or exfiltrating data.
3. Capture a live memory image (RAM dump) of the infected machine to extract the injected code from the hollowed process.
4. Perform a wide EDR hunt across the enterprise using the hash of the initial Delphi dropper.

What to Avoid

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

1. Do not dismiss a Delfinject alert as a generic false positive; it is a clear indicator of an active evasion attempt.
2. Avoid relying solely on static analysis of the Delphi file on disk; the true threat is the payload it injects into memory.

References & External Analysis

• Search "delfinject" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Magania
• Ceeinject
• Negasteal
• Pjzab0Jsupjb
• Nmkfxmdtnmoi

Machine-readable

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