Zylom

Overview

Adware:Win32/Zylom is a deceptive adware framework and Potentially Unwanted Program (PUA) that silently infiltrates endpoints, typically bundled with freeware, to inject intrusive advertisements, hijack browser settings, and harvest user search telemetry for affiliate monetization.

What is Zylom?
To the average user, Zylom is highly visible and deeply frustrating. The browser homepage is forcibly changed, default search engines are locked to unfamiliar domains, and standard websites are flooded with injected banner ads or in-text hyperlinks. For security analysts, Zylom operates on the Pay-Per-Install (PPI) model. It leverages deceptive installation tactics and aggressive persistence mechanisms to ensure the user cannot easily revert their browser settings, guaranteeing continued revenue generation for the attackers.

Infection Vectors & Threat Hunting
Zylom is almost exclusively distributed via deceptive software bundlers. When a user downloads a free PDF editor or media player from a third-party site, the Zylom wrapper executes first. It employs 'Dark Patterns'—pre-checked boxes hidden behind 'Advanced' menus—to gain technical consent. Upon execution, it installs malicious browser extensions and frequently leverages Windows Group Policy (GPO) settings (`ExtensionInstallForcelist`) to lock the rogue extensions in place. It establishes persistence via Registry Run keys and scheduled tasks.

Forensic Analysis & Impact
The primary impact is a severely degraded user experience, compromised browsing privacy, and wasted helpdesk resources. Incident responders will observe anomalous HTTP/HTTPS traffic to known ad-tracking networks. EDR logs will show the initial installer attempting to modify browser preference files (e.g., Chrome's `Preferences` JSON file) and establishing unauthorized Group Policies.

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:

• 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_ZYLOM {
    meta:
        description = "Detects Zylom (advanced_threat)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "zylom" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Zylom Activity
id: e59900024cf16fa4819e67eeb3066c9f
status: experimental
description: Detects generic indicators of the zylom malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*zylom*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Quarantine the endpoint to halt the active exfiltration of browsing telemetry and the downloading of further adware modules.
2. Audit Windows Group Policies and the Registry to remove any forced extension installation policies created by the adware.
3. Deploy an enterprise adware removal tool (e.g., AdwCleaner) to locate and strip the deeply embedded registry hooks and watchdog services.
4. Force a complete reset of all installed web browsers to factory defaults to eradicate the rogue extensions and restore the homepage.

What to Avoid

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

1. Do not rely solely on the browser's 'remove extension' button; Zylom frequently uses GPOs and watchdog services to immediately reinstall itself.
2. Avoid ignoring the infection; adware tracking data is highly detailed and may expose corporate activities or access to internal portals.

References & External Analysis

• Search "zylom" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: advanced_threat)

Explore other malware families in the same category:

• Offerinstall
• Imestartup
• Ytddownloader
• Russoturisto
• Helper

Machine-readable

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