Zeroaccess
Table of Contents
Overview
ZeroAccess (also known worldwide as Sirefef and classified under signatures including Rootkit:Win32/Sirefef, Trojan:Win32/ZeroAccess, and Backdoor:Win32/Sirefef) is one of the most sophisticated and prolific peer-to-peer (P2P) botnets and kernel-mode rootkits in cybersecurity history, active from 2009 until major industry sinkholing disruptions in 2013–2014. ZeroAccess infected over 2 million endpoints globally, monetized primarily through massive Bitcoin mining and search engine click-fraud operations. The malware employs advanced rootkit techniques, overwriting system drivers, modifying Master Boot Records (MBR), creating hidden encrypted NTFS alternate data stream (ADS) volumes, and hooking kernel functions to conceal its presence. It communicates across a decentralized P2P Kad-like mesh network, allowing resilient distribution of binary updates and click-fraud tasks without relying on centralized C2 servers.
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: Rootkit:Win32/Sirefef.A · Trojan:Win32/Zeroaccess.B
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1014 · T1542.003 · T1547.001 · T1055 · T1496
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-KMC | Kernel Memory Integrity Checking | Harden | T1014 | Enable Hypervisor-Protected Code Integrity (HVCI) and UEFI Secure Boot to prevent unsigned kernel driver execution. |
D3-PIAD | Process Injection Analysis & Detection | Detect | T1055 | Monitor cross-process thread creation (CreateRemoteThread) and asynchronous procedure calls (QueueUserAPC). |
D3-PEA | Processor Execution Auditing | Detect | T1496 | Alert on sustained high CPU/GPU utilization by processes originating from temporary user directories and block stratum mining pool ports. |
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_ZEROACCESS_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Zeroaccess"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "zeroaccess" ascii wide nocase
$s2 = "rootkit:win32/sirefef" ascii wide nocase
$s3 = "trojan:win32/zeroaccess" ascii wide nocase
$s4 = "rootkit:win32/zeroaccess" ascii wide nocase
$s5 = "win32/sirefef" ascii wide nocase
$s6 = "backdoor:win32/sirefef" ascii wide nocase
$s7 = "sirefef rootkit" 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 - Zeroaccess (Rootkit) Execution & Triage
id: 54cdccfb-f026-59f0-89de-135b13b0f318
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Zeroaccess 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/zeroaccess
- 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.rootkit
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1014
- attack.t1542_003
- attack.t1547_001
- attack.t1055
- attack.t1496
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_ZEROACCESS_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Zeroaccess 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 = "zeroaccess" 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 - Rootkit:Win32/Sirefef
- Trend Micro Threat Encyclopedia - Rootkit.Win32.Sirefef
- Search "zeroaccess" on VirusTotal (External Analysis)
- Search "zeroaccess" on Any.Run (Sandbox Sandbox)
- Search "zeroaccess" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is the ZeroAccess (Sirefef) rootkit?
ZeroAccess is a landmark kernel-mode rootkit and P2P botnet that infected millions of computers for click-fraud and Bitcoin mining.
How does ZeroAccess conceal itself on Windows?
It overwrites legitimate system drivers, creates hidden NTFS encrypted volumes, and hooks kernel functions to hide files and network traffic.
How does the ZeroAccess botnet communicate without central servers?
It uses a decentralized Peer-to-Peer (P2P) UDP protocol where infected nodes discover and share tasks with each other directly.
What malicious payloads were executed by ZeroAccess?
It deployed CPU/GPU Bitcoin mining modules and click-fraud engines that hijacked search results and generated millions in fraudulent ad revenue.
How was the ZeroAccess botnet disrupted?
Microsoft, Europol, and industry partners executed coordinated legal and technical sinkholing operations in December 2013 to sever the P2P network.
How do I remove the Zeroaccess Rootkit from Windows?
Manual removal of Zeroaccess 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.
Is Zeroaccess a virus or a Rootkit?
Zeroaccess is classified as a Rootkit. Unlike traditional viruses that infect files, modern malware like Zeroaccess typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Zeroaccess infection?
Symptoms of Zeroaccess 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 Rootkits
Want to prevent Zeroaccess and similar threats from compromising your organization? Read our comprehensive defensive guide: Rootkit & Bootkit Protection.
📣 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/zeroaccess.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.