{
  "family": "computty",
  "sample_count": 1,
  "category": "trojan",
  "description": "<h3>Executive Summary</h3>\nComputty (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.\n\n<h3>Infection Vector and Technical Capabilities</h3>\nThe 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.\n\nUpon 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:\n<ul>\n<li><strong>Credential Harvesting:</strong> The core malicious functionality is to intercept the usernames, passwords, and SSH private keys entered by the administrator when authenticating to a remote server.</li>\n<li><strong>Covert Exfiltration:</strong> 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.</li>\n<li><strong>Evasion:</strong> 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.</li>\n</ul>\n\n<h3>Threat Assessment</h3>\nThe 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).\n\n<h3>Incident Response and Remediation</h3>\n<ul>\n<li><strong>Immediate Global Key Rotation:</strong> 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.</li>\n<li><strong>Endpoint Sweeps and File Hashing:</strong> 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.</li>\n<li><strong>Network Segmentation and MFA:</strong> Enforce Multi-Factor Authentication (MFA) for all administrative SSH connections, ensuring that stolen credentials alone are insufficient for access.</li>\n</ul>",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [
    "HackTool.PuTTY",
    "Trojan.PuTTY.Modified",
    "PWS.PuTTY"
  ],
  "enrichment_level": "insufficient_information",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1552.004",
    "T1056.001",
    "T1556"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-07-01T17:25:49Z",
  "type": "HackTool / Credential Stealer",
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}