Delfinject
Table of Contents
Overview
DelfInject (cataloged across security intelligence feeds under signatures including Trojan:Win32/DelfInject, VirTool:Win32/DelfInject, and Trojan.DelfInject) is an evasive Delphi-compiled trojan loader, runtime crypter, and process injector active since 2014. Widely utilized in crimeware campaigns to distribute commodity remote access trojans (RATs) and banking malware, DelfInject encapsulates raw binary payloads inside an encrypted PE overlay or Delphi resource section. Upon launch, DelfInject performs anti-debugging and anti-VM checks (inspecting RDTSC timing, registry hardware keys, and VMware/VirtualBox drivers). It then unhooks user-mode NT APIs (ntdll.dll), allocates executable memory in legitimate target processes like svchost.exe or explorer.exe via VirtualAllocEx and WriteProcessMemory, and executes the decrypted payload using CreateRemoteThread or NtQueueApcThread.
Known aliases
Threat reports may refer to this family under multiple names:
Family Pedigree & Lineage
Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:
Known Derivatives & Downstream Variants: Trojan:Win32/Delfinject.A · Virtool:Win32/Delfinject.Gen
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1055.001 · T1055.004 · T1027 · T1497.001 · T1547.001
MITRE D3FEND™ Defensive Countermeasures
Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):
| D3FEND ID | Countermeasure Name | Tactic | Countered ATT&CK | Defensive Guidance |
|---|---|---|---|---|
D3-BDA | Binary De-obfuscation & Unpacking | Analyze | T1027 | Utilize memory dump scanners and entropy inspection to unpack encrypted stagers during process creation. |
D3-DIA | DLL Injection Analysis | Detect | T1055.001 | Monitor remote thread creation (CreateRemoteThread) and unauthorized DLL loading into core Windows processes (svchost.exe, explorer.exe). |
D3-PIAD | Process Injection Analysis & Detection | Detect | T1055.004 | Monitor cross-process thread creation (CreateRemoteThread) and asynchronous procedure calls (QueueUserAPC). |
D3-EED | Execution Environment Detection | Detect | T1497.001 | Configure malware sandboxes to emulate legitimate hardware metrics, realistic mouse movements, and valid system uptimes. |
D3-RPM | Registry Persistence Monitoring | Detect | T1547.001 | Audit and restrict write privileges to user and machine-level Registry Run/RunOnce keys using Endpoint Privilege Management. |
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:
Tier 1 Primitive Artifact Rule (Fast Triage)
Matches raw strings and file markers. Vulnerable to binary repacking and simple obfuscation.
rule MALWARE_WIN_DELFINJECT_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Delfinject"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "delfinject" ascii wide nocase
$s2 = "trojan:win32/delfinject" ascii wide nocase
$s3 = "virtool:win32/delfinject" ascii wide nocase
$s4 = "trojan.delfinject" ascii wide nocase
$s5 = "win32/delfinject" ascii wide nocase
$s6 = "trojan:win32/delfinject.a" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Tier 2 Behavioral Context Rule (Process Chains & Sigma)
Tracks parent-child process anomalies and suspicious scripting telemetry. Resilient against file renames.
title: SystemHelpDesk Detection - Delfinject (Trojan) Execution & Triage
id: 5360e043-b61f-57db-a506-d063b833c435
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Delfinject malware family. Detects suspicious execution from temporary
user directories with hidden window flags and background transfer utilities.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/delfinject
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1055_001
- attack.t1055_004
- attack.t1027
- attack.t1497_001
- attack.t1547_001
logsource:
category: process_creation
product: windows
detection:
selection_process:
Image|endswith:
- \cmd.exe
- \powershell.exe
- \cscript.exe
- \wscript.exe
CommandLine|contains:
- AppData\Local\Temp
- -WindowStyle Hidden
- /e:jscript
- bitsadmin /transfer
condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: mediumTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_DELFINJECT_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Delfinject 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 = "delfinject" 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
}References & External Analysis
- Microsoft Defender Threat Encyclopedia - Trojan:Win32/DelfInject
- Trend Micro Threat Encyclopedia - Trojan.Win32.DelfInject
- Search "delfinject" on VirusTotal (External Analysis)
- Search "delfinject" on Any.Run (Sandbox Sandbox)
- Search "delfinject" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Trojan:Win32/DelfInject?
DelfInject is a Delphi-compiled trojan injector and crypter that executes encrypted secondary malware inside legitimate processes.
How does DelfInject evade sandbox detection?
It performs RDTSC CPU cycle timing checks, searches for virtual machine drivers, and delays execution using high-resolution sleep routines.
What injection methods are used by DelfInject?
It uses VirtualAllocEx, WriteProcessMemory, and CreateRemoteThread to inject shellcode into svchost.exe or explorer.exe.
What secondary malware is commonly delivered by DelfInject?
DelfInject is frequently used to deliver remote access trojans (njRAT, AsyncRAT), info-stealers, and banking trojans.
How can defenders detect DelfInject activity?
Monitor for cross-process memory allocations and remote thread creation targeting svchost.exe using behavioral EDR tools.
How do I remove Delfinject from Windows?
Manual removal of Delfinject is highly discouraged as it may leave persistence mechanisms intact. We recommend disconnecting the device from the internet and utilizing a professional incident response service or enterprise-grade EDR software to conduct a full forensic sweep.
What are the main symptoms of a Delfinject infection?
Symptoms of Delfinject can include unexpected system slowness, unauthorized outbound network traffic to unknown IP addresses, disabled security software, and suspicious background processes running from AppData or Temp directories.
Protect Your Network Against Trojans
Want to prevent Delfinject and similar threats from compromising your organization? Read our comprehensive defensive guide: Banking Trojan Protection for Businesses.
📣 Threat Intel Correction or Update?
Notice an outdated IOC, unlisted alias, or disputed attribution? Threat researchers are invited to propose an update on GitHub or contact the SystemHelpDesk research desk. All community revisions are credited in our public CHANGELOG.
Machine-readable
Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/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.