{
  "family": "zero",
  "sample_count": 1,
  "category": "ransomware",
  "description": "<h3>Executive Summary</h3>\nWhile \"Zero\" can occasionally refer to minor ransomware variants, in enterprise security contexts, it most commonly refers to the ZeroAccess botnet (also known as Sirefef). ZeroAccess is a highly sophisticated, kernel-level rootkit designed to completely subjugate Windows systems. Its primary objective is to create a massive peer-to-peer (P2P) botnet utilized for highly profitable click fraud campaigns and Bitcoin mining, operating entirely invisibly to the user.\n\n<h3>Infection Vector and Technical Capabilities</h3>\nZeroAccess is typically distributed via exploit kits (like Blackhole) hosted on compromised websites, which silently exploit unpatched browser or Java vulnerabilities. It is also distributed via malicious software bundlers on peer-to-peer networks.\n\nUpon execution, ZeroAccess employs advanced, highly destructive rootkit techniques:\n<ul>\n<li><strong>Kernel-Level Hooking:</strong> The malware injects itself deep into the Windows operating system core (Ring 0). It actively overwrites critical system drivers (like `tcpip.sys`) to intercept and manipulate network traffic.</li>\n<li><strong>Security Software Neutralization:</strong> ZeroAccess aggressively hunts for and terminates processes associated with antivirus and EDR solutions. It also actively blocks updates to Windows Defender and other security tools.</li>\n<li><strong>Hidden Volumes:</strong> It creates hidden, encrypted volumes within the Windows file system (often masquerading as Recycle Bin data) to store its configuration files, downloaded payloads, and the stolen click-fraud data, making it invisible to standard file explorers and basic AV scans.</li>\n<li><strong>P2P Communication:</strong> Rather than relying on a centralized C2 server that can be easily taken down, infected nodes communicate directly with each other via a custom P2P protocol to receive updates and new instructions.</li>\n</ul>\n\n<h3>Threat Assessment</h3>\nA ZeroAccess infection is a critical compromise of system integrity. The malware's ability to operate at the kernel level means it completely controls the operating system's reality. It causes severe network congestion (due to P2P chatter and click fraud traffic) and leaves the machine completely defenseless against other malware.\n\n<h3>Incident Response and Remediation</h3>\n<ul>\n<li><strong>Immediate Network Severance:</strong> Isolate the endpoint to halt the click fraud traffic and prevent it from acting as a node in the P2P botnet.</li>\n<li><strong>Do Not Attempt Cleaning:</strong> Because ZeroAccess overwrites critical system drivers and utilizes encrypted rootkit volumes, attempting to manually clean the infection or run standard AV removal tools will almost certainly result in a permanently unbootable system (Blue Screen of Death).</li>\n<li><strong>Total Re-imaging:</strong> The only secure and reliable remediation for a ZeroAccess/Sirefef infection is a complete bare-metal wipe of the hard drive and a fresh OS installation from a known-good baseline.</li>\n</ul>",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [
    "Rootkit.ZeroAccess",
    "Trojan.Sirefef",
    "Win32/ZeroAccess"
  ],
  "enrichment_level": "insufficient_information",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1014",
    "T1562.001",
    "T1090.003",
    "T1564"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-07-02T07:12:52Z",
  "type": "Rootkit / Botnet",
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}