Sharer
Table of Contents
Overview
Executive Summary
Sharer (often detected as Worm.P2P.Sharer or Trojan.Sharer) represents a family of legacy worms specifically engineered to exploit the decentralized nature of Peer-to-Peer (P2P) file-sharing networks (such as eMule, Kazaa, Limewire, or BitTorrent). By masquerading as highly desirable, pirated content, Sharer tricks users into downloading and executing the malware, subsequently hijacking the user's P2P client to distribute itself to thousands of other victims.Infection Vector and Technical Capabilities
The primary infection vector is entirely reliant on user deception. The malware is uploaded to P2P networks with enticing, frequently changing filenames (e.g., "Windows_10_Crack.exe", "Photoshop_Keygen.exe", or titles of recently released movies/music). Upon execution, Sharer focuses on rapid, automated propagation:- P2P Client Hijacking: The worm actively searches the infected system for the installation directories and shared folders of popular P2P clients.
- Automated Seeding: Once the shared folders are located, the worm copies its executable into them, often generating hundreds of copies with dynamically generated, clickbait filenames. It then forces the P2P client to actively "seed" (upload) these malicious files to the broader network.
- Secondary Payloads: While the primary function is propagation, Sharer worms frequently act as loaders, downloading secondary payloads such as Adware (to generate pay-per-install revenue for the author) or Info-stealers (to harvest credentials).
Threat Assessment
While the prominence of traditional P2P networks has declined in favor of streaming services, the tactic remains viable on modern torrent networks. A Sharer infection exposes the corporate network to significant legal liability (due to the active distribution of pirated/malicious files) and serves as an open door for more severe, secondary malware infections.Remediation and Eradication
- Network Blocking (P2P): The most effective defense is perimeter-level blocking. Enterprise firewalls and web gateways must be configured to strictly block the protocols and ports associated with P2P file sharing (e.g., BitTorrent).
- Application Control: Enforce strict application whitelisting to prevent standard users from installing unauthorized P2P client software on corporate assets.
- Endpoint Cleanup: Utilize enterprise anti-malware solutions to scan for and remove the Sharer executables, paying special attention to user profile directories (like `%AppData%`) where the worm often hides its payload and generated copies.
Known aliases
Threat reports may refer to this family under multiple names:
MITRE ATT&CK Techniques
Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:
| Technique | Name | Tactic | Official Spec |
|---|---|---|---|
T1566 | Phishing | Initial Access | ATT&CK ↗ |
T1059 | Command and Scripting Interpreter | Execution | ATT&CK ↗ |
T1105 | Ingress Tool Transfer | Command and Control | ATT&CK ↗ |
Tactical Mitigations
Based on the techniques used by this family, consider the following defensive strategies:
- T1059: Restrict execution of scripting languages such as PowerShell, VBScript, or Python to authorized administrators. Enforce Script Block Logging.
- T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
- T1566: Implement email filtering, Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and DMARC. Conduct user phishing awareness training.
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-SEA | Script Execution Analysis | Detect | T1059 | Analyze script block syntax and command arguments at runtime to detect malicious automation. |
D3-NTI | Network Traffic Inspection | Detect | T1105 | Inspect deep packet payloads for anomalous staging binaries and unauthorized egress protocols. |
D3-ESF | Email Sender Authentication & Filtering | Verify | T1566 | Enforce strict SPF, DKIM, and DMARC rejecting p=reject alongside real-time malicious link rewriting. |
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_SHARER_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Sharer"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "sharer" ascii wide nocase
$s2 = "worm.p2p.sharer" ascii wide nocase
$s3 = "trojan.p2p" ascii wide nocase
$s4 = "win32/sharer" 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 - Sharer (Trojan) Execution & Triage
id: 654ebacc-2abc-5190-a1b1-3a00bbd443e7
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Sharer 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/sharer
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1566
- attack.t1059
- attack.t1105
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_SHARER_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Sharer 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 = "sharer" 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.
- Sever network connectivity for the flagged endpoint to terminate persistent command-and-control (C2) communication channels and stop Sharer from retrieving secondary stage payloads.
- Capture process memory triage to detect and terminate malicious threads injected by Sharer into legitimate system processes such as explorer.exe or svchost.exe.
- Audit Windows Registry Run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run) and Task Scheduler entries to locate and purge Sharer persistence hooks.
- Deploy updated enterprise EDR detection signatures and conduct an out-of-band endpoint scan to isolate dropped binaries and staged payloads.
- Rotate all credentials, domain user passwords, and session cookies active on the system during the Sharer execution timeframe.
What to Avoid
Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.
- Do not assume the incident is resolved simply because an antivirus tool removed the initial Sharer dropper; always verify that secondary payloads and persistence hooks have been eradicated.
- Avoid logging in with Domain Admin or privileged credentials on a machine suspected of running Sharer until memory triage is complete.
- Do not delay host isolation; automated lateral movement and credential dumping can occur within minutes of initial execution.
References & External Analysis
- Search "sharer" on VirusTotal (External Analysis)
- Search "sharer" on Any.Run (Sandbox Sandbox)
- Search "sharer" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Sharer and what threat category does it belong to?
Sharer is classified as a Trojan. Documented across security telemetry, it is engineered to execute unauthorized operations, establish persistent footholds on target endpoints, and facilitate malicious campaigns targeting enterprise and individual environments.
How does Sharer establish persistence and evade defensive controls?
Sharer typically establishes persistence through registry run keys, scheduled tasks, or service installations, while evading signature-based antivirus solutions through code obfuscation, memory injection, or anti-analysis sandbox checks.
What are the essential incident response steps for mitigating a Sharer compromise?
Security teams responding to Sharer should immediately isolate affected endpoints from the network, perform memory triage to capture volatile forensic artifacts, audit registry and startup persistence mechanisms, revoke exposed user credentials, and restore systems from verified, clean backups.
What secondary payloads and staging behaviors are commonly associated with Worm.P2P.Sharer?
Worm.P2P.Sharer frequently operates as a loader or dropper designed to establish a foothold before downloading and executing secondary high-impact malware payloads. Depending on the threat actor's objectives, these dropped modules can range from ransomware and banking injects to modular infostealers and remote management backdoors.
How can security operations teams effectively detect and hunt for Worm.P2P.Sharer across enterprise endpoints?
Defenders should hunt for Worm.P2P.Sharer by deploying behavioral endpoint detection and response (EDR) rules that monitor suspicious process spawning (such as cmd.exe or powershell.exe spawned from office documents or temporary directories), anomalous outbound network connections from non-browser binaries, and unauthorized modifications to Windows Run keys and scheduled task registries.
How do I remove the Sharer Trojan from Windows?
Manual removal of Sharer 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 Sharer a virus or a Trojan?
Sharer is classified as a Trojan. Unlike traditional viruses that infect files, modern malware like Sharer typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Sharer infection?
Symptoms of Sharer 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 Trojans
Want to prevent Sharer and similar threats from compromising your organization? Read our comprehensive defensive guide: Banking Trojan Protection for Businesses.
📣 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/sharer.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.