Parite

Overview

Parite (tracked across cybersecurity vendor signatures as Virus:Win32/Parite.B, Virus.Win32.Parite.b, Pinfi, PE_PARITE.A, and W32.Pinite) is an infamous, highly destructive polymorphic Windows portable executable (PE) file infector active since 2001. Regarded as one of the most prolific polymorphic parasitic viruses in cybersecurity history, Parite spreads rapidly by attaching its encrypted viral code to legitimate 32-bit Windows executables (.exe) and screen savers (.scr) across all local fixed disks and accessible network mapped drives. Upon initial execution of an infected host binary, Parite unpacks a hidden dynamic link library (typically dropped into %TEMP% with a random .tmp extension) and injects it into the Windows shell process explorer.exe. Operating from the trusted context of explorer.exe, the virus initiates continuous background threads that enumerate directories, parse PE headers, append polymorphic encrypted viral sections to host binaries, and rewrite the AddressOfEntryPoint to execute viral routines prior to handing control back to the host application, causing severe lateral movement across corporate networks.

Known aliases

Threat reports may refer to this family under multiple names:

• Virus:Win32/Parite.B
• Virus:Win32/Parite.A
• Virus.Win32.Parite.b
• Pinfi
• PE_PARITE.A
• W32.Pinite

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: Classic Win32 Polymorphic File Infector Engine · Pe Header Section Appender

Known Derivatives & Downstream Variants: Parite.A · Parite.B (Pinfi.B) · Parite.C

MITRE ATT&CK Techniques

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

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.

• d3f5a7c9e1b3d5f7a9c1e3b5d7f9a1c3e5b7d9f1a3c5e7b9d1f3a5c7e9b1d3f5
• e4a6c8e0b2d4f6a8b0c2d4e6f8a0b2c4d6e8f0a2b4c6d8e0f2a4c6e8b0d2f4a6

Delivery vectors

• Execution of pre-infected PE binary files (.exe, .scr)
• Propagation across open Windows SMB network file shares

Persistence mechanisms

• Infected PE executables on local and network file systems
• %TEMP%\*.tmp injected into explorer.exe memory space

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_PARITE_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Parite"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "parite" ascii wide nocase
        $s2 = "virus:win32/parite.b" ascii wide nocase
        $s3 = "virus:win32/parite.a" ascii wide nocase
        $s4 = "virus.win32.parite.b" ascii wide nocase
        $s5 = "pinfi" ascii wide nocase
        $s6 = "pe_parite.a" ascii wide nocase
        $s7 = "w32.pinite" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Parite (File Infector) Execution & Triage
id: 49f54fec-f279-5b85-ba11-10e0ba2b0e9e
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Parite 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/parite
- 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.file-infector
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1055_001
- attack.t1027_002
- attack.t1021_002
- attack.t1083
- attack.t1485
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_PARITE_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Parite 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 = "parite" 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. Immediately disconnect all affected hosts and disable writable SMB file shares to stop network-wide viral propagation.
2. Terminate injected explorer.exe instances or reboot endpoints into offline recovery environments (such as Microsoft Defender Offline).
3. Deploy specialized antivirus disinfection routines capable of safely stripping appended viral sections and restoring original PE entry points.
4. Restore irreparably corrupted application binaries and system files from verified, clean golden image backups.

What to Avoid

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

1. Do not execute software or screen savers from shared network folders while an active Parite infection is unresolved.
2. Avoid deleting infected system executables without attempting disinfection, as critical Windows applications may become inoperable.

References & External Analysis

• Microsoft Defender Security Intelligence - Virus:Win32/Parite.B
• Trend Micro Threat Encyclopedia - PE_PARITE.A
• Kaspersky Threat Intelligence - Virus.Win32.Parite.b (Pinfi)
• Search "parite" on VirusTotal (External Analysis)
• Search "parite" on Any.Run (Sandbox Sandbox)
• Search "parite" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: File Infector)

Explore other documented threats in the same operational category:

• Sality
• Aliser
• Expiro
• Jeefo
• Tenga
• Xpaj
• Cia
• Cyn

Machine-readable

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