Computty
Overview
Executive Summary
Computty (often detected as HackTool.PuTTY.Modified or Trojan.PuTTY) is a malicious modification of the legitimate, highly popular open-source SSH and Telnet client, PuTTY. Threat actors take the legitimate PuTTY source code, inject malicious functionality (usually a credential stealer or a backdoor), recompile it, and distribute it to system administrators, allowing the attackers to intercept highly privileged authentication credentials.Infection Vector and Technical Capabilities
The modified PuTTY executable is typically distributed via spear-phishing campaigns targeting IT staff, or by hosting the backdoored software on lookalike "typosquatting" domains designed to mimic the official PuTTY download page. Upon execution, the tool functions exactly like the legitimate PuTTY client, allowing the administrator to successfully connect to remote servers. However, it operates with severe malicious intent:- Credential Harvesting: The core malicious functionality is to intercept the usernames, passwords, and SSH private keys entered by the administrator when authenticating to a remote server.
- Covert Exfiltration: The stolen credentials are silently logged and periodically transmitted to an attacker-controlled command-and-control (C2) server, usually over HTTP or SMTP to blend in with normal traffic.
- Evasion: Because the underlying code is the legitimate PuTTY client, the backdoored executable often evades basic signature-based antivirus detection, appearing as a standard administrative tool.
Threat Assessment
The compromise of an administrative tool like PuTTY is a catastrophic security incident. By stealing SSH credentials, the attackers gain direct, highly privileged access to the organization's core infrastructure (Linux servers, firewalls, routers), entirely bypassing perimeter defenses and multi-factor authentication (if keys are stolen).Incident Response and Remediation
- Immediate Global Key Rotation: If a modified PuTTY executable is discovered, assume that every server the administrator connected to has been compromised. Immediately revoke and regenerate all SSH keys and passwords associated with that administrator.
- Endpoint Sweeps and File Hashing: Utilize enterprise EDR to sweep the network for the specific hash of the modified PuTTY binary. Remove the malicious executable and enforce the usage of centrally deployed, verified IT tools.
- Network Segmentation and MFA: Enforce Multi-Factor Authentication (MFA) for all administrative SSH connections, ensuring that stolen credentials alone are insufficient for access.
Known aliases
Threat reports may refer to this family under multiple names:
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1552.004 T1056.001 T1556
Tactical Mitigations
Based on the techniques used by this family, consider the following defensive strategies:
- T1056.001: Implement Endpoint Detection and Response (EDR) to monitor for suspicious API calls related to keystroke interception. Enforce Multi-Factor Authentication (MFA) to render stolen passwords useless.
Generated Detections (Boilerplate)
These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.
YARA Rule
rule MALWARE_WIN_COMPUTTY {
meta:
description = "Detects Computty (trojan)"
author = "SystemHelpdesk Boilerplate Generator"
date = "2026-07-06"
strings:
$s1 = "computty" ascii wide nocase
$s2 = "hacktool.putty" ascii wide nocase
$s3 = "trojan.putty.modified" ascii wide nocase
$s4 = "pws.putty" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Sigma Rule
title: Suspicious Computty Activity
id: 9090a93b52ca2e4d8923443ad9c3df05
status: experimental
description: Detects generic indicators of the computty malware family.
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith:
- '\cmd.exe'
- '\powershell.exe'
CommandLine|contains:
- "*computty*"
- "*hacktool.putty*"
- "*trojan.putty.modified*"
- "*pws.putty*"
condition: selection
level: mediumReferences & External Analysis
- Search "computty" on VirusTotal (External Analysis)
Frequently Asked Questions
How do I remove the Computty Trojan from Windows?
Manual removal of Computty 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 Computty a virus or a Trojan?
Computty is classified as a Trojan. Unlike traditional viruses that infect files, modern malware like Computty typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Computty infection?
Symptoms of Computty 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.
Related Families (Category: trojan)
Explore other malware families in the same category:
Protect Your Network Against Trojans
Want to prevent Computty and similar threats from compromising your organization? Read our comprehensive defensive guide: Banking Trojan Protection.
Machine-readable
Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/api/computty.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.