Wintrim

Overview

Trojan:Win32/Wintrim is a persistent, stealthy trojan often functioning as an adware clicker or a backdoor designed to breach endpoint defenses and securely deliver secondary payloads. It is known to heavily inject intrusive advertisements or silently click on hidden ads to generate fraudulent revenue for the attackers.

Understanding Wintrim
To an end-user, a Wintrim infection is typically noticed through severe system sluggishness, unexpected pop-up windows appearing even when browsers are closed, or redirected web searches. For threat intelligence analysts, Wintrim represents a significant nuisance and a potential staging mechanism for further infections, as adware botnets are frequently rented out to distribute more severe malware.

Execution and Evasion Strategies
Wintrim is commonly distributed via massive malspam campaigns containing weaponized attachments, software bundles (`T1189`), or through exploit kits. Upon execution, it utilizes packing to evade static antivirus signatures. It drops a randomized executable into the `%Temp%` or `%AppData%` directory. It establishes persistence by creating a hidden scheduled task or modifying the Registry Run keys. Wintrim frequently injects its ad-clicking or downloading routine into legitimate system processes (like `explorer.exe` or `svchost.exe`) (`T1055`) to mask its outbound network traffic and hide its activity from the user.

Indicators of Compromise (IoCs)
Threat hunters should investigate EDR alerts related to 'Suspicious Process Injection' or 'Anomalous Child Process Spawning'. Network logs will often reveal Wintrim reaching out to known advertising networks or compromised domains using encrypted HTTPS traffic, often generating massive amounts of automated clicks. The presence of unexpected, hidden scheduled tasks designed to execute randomly named binaries in the user's profile is a strong IoC.

MITRE ATT&CK Techniques

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

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

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

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_WINTRIM_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Wintrim"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "wintrim" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Wintrim (Trojan) Execution & Triage
id: f2e6298b-5296-581d-986e-084192672880
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Wintrim 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/wintrim
- 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.t1189
- attack.t1027
- attack.t1055
- attack.t1105
- 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: medium

rule MALWARE_WIN_WINTRIM_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Wintrim 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 = "wintrim" 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 immediately to prevent Wintrim from generating ad fraud traffic or downloading secondary payloads.
2. Audit the Windows Task Scheduler and Registry Run keys to identify and remove the Wintrim persistence mechanisms.
3. Review firewall and proxy logs to identify the C2 or ad-network domains Wintrim attempted to contact, and block them enterprise-wide.
4. Run a comprehensive anti-malware and adware removal scan to ensure all injected components are removed from the system.

What to Avoid

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

1. Do not close an incident simply because the initial Wintrim dropper was quarantined; always verify if secondary payloads were downloaded.
2. Avoid relying solely on manual file deletion, as the injected processes will likely just recreate the dropped binaries.

References & External Analysis

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

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Lmkfrhivlcfba
• Ceeinject
• Sign0Fmisery
• Fuery
• Fakeplayer
• Hesv
• Zpevdo
• Casper

Machine-readable

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