Renos
Table of Contents
Overview
Renos (cataloged across security intelligence feeds under signatures including TrojanDownloader:Win32/Renos, Trojan.Renos, and Trojan-Downloader.Win32.Renos) is a landmark family of trojan downloaders active from 2007 to 2011, engineered to deliver rogue antivirus software and scareware (such as FakeSpypro, Antivirus 2009, and System Defender). Delivered predominantly through malicious advertising networks (malvertising), fake video codec prompts, and compromised websites via drive-by downloads, Renos silently establishes an initial foothold on Windows systems. Once executed, Renos contacts remote distribution servers over HTTP, downloads secondary scareware installers, disables Windows security alerts, and modifies the Windows Registry Run keys to ensure the dropped rogue software runs at startup to coerce victims into purchasing fraudulent licenses.
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:
Derived From / Upstream Ancestry: Winwebsec Rogue Security Syndicate
Known Derivatives & Downstream Variants: Trojandownloader:Win32/Renos.A · Trojandownloader:Win32/Renos.B
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1105 · T1562.001 · T1547.001 · T1082 · T1071.001
Tactical Mitigations
Based on the techniques used by this family, consider the following defensive strategies:
- T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.
- T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
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-WAF | Web Content Filtering & Inspection | Filter | T1071.001 | Block newly registered domains (NRDs) and inspect HTTP Host and URI headers for known C2 profiles. |
D3-SDA | System Discovery Analysis | Detect | T1082 | Alert on rapid enumerations of systeminfo, hostname, and registry hardware trees in short intervals. |
D3-NTI | Network Traffic Inspection | Detect | T1105 | Inspect deep packet payloads for anomalous staging binaries and unauthorized egress protocols. |
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. |
D3-STA | Security Tool Anti-Tamper Enforcement | Harden | T1562.001 | Block unauthorized modification of antivirus registry flags and prevent stopping security agent services. |
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_RENOS_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Renos"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "renos" ascii wide nocase
$s2 = "trojandownloader:win32/renos" ascii wide nocase
$s3 = "trojan.renos" ascii wide nocase
$s4 = "trojan-downloader.win32.renos" ascii wide nocase
$s5 = "win32/renos" ascii wide nocase
$s6 = "fakespypro downloader" 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 - Renos (Trojan Downloader) Execution & Triage
id: c91e9c8d-697c-569c-a063-a09571a8fd07
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Renos 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/renos
- 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.trojan-downloader
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1105
- attack.t1562_001
- attack.t1547_001
- attack.t1082
- attack.t1071_001
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_RENOS_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Renos 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 = "renos" 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 - TrojanDownloader:Win32/Renos
- Trend Micro Threat Encyclopedia - Trojan.Win32.Renos
- Search "renos" on VirusTotal (External Analysis)
- Search "renos" on Any.Run (Sandbox Sandbox)
- Search "renos" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is TrojanDownloader:Win32/Renos?
Renos is a landmark trojan downloader family that dropped rogue antivirus programs and scareware onto Windows systems.
What rogue software was delivered by Renos?
Renos delivered infamous scareware suites such as FakeSpypro, Antivirus 2009, System Defender, and Winwebsec.
How did Renos infect computers?
Through malicious banner ads (malvertising), fake video player codec popups, and drive-by download exploits on compromised sites.
How does Renos establish persistence on Windows?
It writes autostart entries in HKCU\Software\Microsoft\Windows\CurrentVersion\Run and registers background scheduled tasks.
How was Renos eradicated from infected systems?
Boot into Safe Mode, run an on-demand antimalware scanner like Microsoft Defender or Malwarebytes, and delete rogue Run registry keys.
How do I remove the Renos Trojan_Downloader from Windows?
Manual removal of Renos 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 Renos a virus or a Trojan_Downloader?
Renos is classified as a Trojan_Downloader. Unlike traditional viruses that infect files, modern malware like Renos typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Renos infection?
Symptoms of Renos 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 Trojan_Downloaders
Want to prevent Renos 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/renos.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.