Icloader

Overview

ICLoader (identified across vendor detection engines as PUA:Win32/ICLoader, Trojan:Win32/ICLoader, and PUP.Optional.InstallCore) is an aggressive software bundler and pay-per-install (PPI) loader linked to the InstallCore distribution network and analyzed by Microsoft Defender and Malwarebytes. Operating primarily through deceptive software distribution sites, ICLoader disguises itself as an official setup wizard for freeware applications, utility drivers, and media converters. Upon execution, the loader contacts central advertising servers to dynamically fetch an installer configuration manifest containing secondary promotional applications. Utilizing deceptive installation dialogs with pre-checked consent boxes and obscure rejection prompts, ICLoader downloads and executes unwanted third-party tools, browser extensions, adware components, and system cleaners. To ensure continued execution of deployed affiliate tools, ICLoader writes persistence keys to HKCU\Software\Microsoft\Windows\CurrentVersion\Run and schedules background Windows tasks. Its operations degrade endpoint performance, alter browser security configurations, and introduce substantial attack surface exposure.

Known aliases

Threat reports may refer to this family under multiple names:

• PUA:Win32/ICLoader
• Trojan:Win32/ICLoader
• Win32/ICLoader
• PUP.Optional.ICLoader
• InstallCore.ICLoader
• Adware:Win32/InstallCore

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Derived From / Upstream Ancestry: Installcore_Monetization_Framework

Known Derivatives & Downstream Variants: Installcore.Gen · Icloader.Variant

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):

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• 2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c
• 3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d

Delivery vectors

• Deceptive freeware mirrors and fake software download landing pages
• Affiliate marketing pay-per-install bundles disguised as media utilities

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\ICLoaderTray
• Scheduled Task created via schtasks /create /tn 'ICLoaderMaintenance' /tr '%AppData%\ICLoader\icupd.exe'

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_ICLOADER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Icloader"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "icloader" ascii wide nocase
        $s2 = "pua:win32/icloader" ascii wide nocase
        $s3 = "trojan:win32/icloader" ascii wide nocase
        $s4 = "win32/icloader" ascii wide nocase
        $s5 = "pup.optional.icloader" ascii wide nocase
        $s6 = "installcore.icloader" ascii wide nocase
        $s7 = "adware:win32/installcore" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Icloader (Pua) Execution & Triage
id: 1f610ac7-a5ec-51a4-b468-6d4c452ec2fc
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Icloader 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/icloader
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-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.pua
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1189
- attack.t1105
- attack.t1204_002
- attack.t1053_005
- 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_ICLOADER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Icloader 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 = "icloader" 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. Quarantine the endpoint to halt ongoing background downloads of secondary adware packages.
2. Audit the Windows Add/Remove Programs list and uninstall software installed during the exact timeframe of the ICLoader execution.
3. Delete persistent scheduled tasks and registry Run keys associated with InstallCore / ICLoader.
4. Run an enterprise endpoint antimalware scan to purge lingering browser hijackers and tracking adware.

What to Avoid

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

1. Do not allow users to download utilities from third-party mirrors that use proprietary wrapper executables.
2. Avoid relying on standard software uninstallation wizards provided by bundled applications, as they often leave persistent background updaters.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - PUA:Win32/ICLoader Analysis
• Malwarebytes Labs Threat Intelligence - PUP.Optional.InstallCore / ICLoader
• NIST National Vulnerability Database - CVE-2015-1641 Overview
• Search "icloader" on VirusTotal (External Analysis)
• Search "icloader" on Any.Run (Sandbox Sandbox)
• Search "icloader" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Pua)

Explore other documented threats in the same operational category:

• Outbrowse
• Onesystemcare
• Tweakbitdu
• Systweak
• Appset
• Uniblue
• 4Shared
• Optimizer

Machine-readable

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