{
  "family": "mailbot",
  "sample_count": 1,
  "category": "ransomware",
  "description": "<h3>Executive Summary</h3>\nMailbot is a malicious Trojan with robust botnet capabilities, specifically engineered to convert infected Windows systems into high-volume spam relays. It is frequently utilized by cybercriminal organizations to distribute massive volumes of pharmaceutical spam, phishing lures, and malicious attachments (often delivering secondary malware like ransomware or info-stealers) while obscuring the true origin of the attack.\n\n<h3>Infection Vector and Technical Capabilities</h3>\nMailbot is predominantly distributed through the very mechanism it facilitates: socially engineered spam campaigns containing malicious attachments or drive-by downloads originating from compromised websites.\n\nUpon successful execution, Mailbot operates with a focus on establishing a covert spam relay:\n<ul>\n<li><strong>Botnet Registration:</strong> The trojan immediately communicates with its command-and-control (C2) server, registering the compromised machine's IP address and bandwidth capacity, effectively enrolling the host into the spam botnet.</li>\n<li><strong>SMTP Engine Installation:</strong> Mailbot does not rely on the user's email client (like Outlook). Instead, it contains its own built-in SMTP (Simple Mail Transfer Protocol) engine. This allows it to send thousands of emails directly to recipient mail servers, bypassing local email security controls.</li>\n<li><strong>Dynamic Configuration:</strong> The C2 server continuously updates the infected host with new spam templates, lists of target email addresses, and lists of compromised SMTP proxies to use for the outbound campaigns.</li>\n</ul>\n\n<h3>Threat Assessment</h3>\nA Mailbot infection severely degrades local network performance by saturating outbound bandwidth. More critically, because the spam originates from the organization's public IP address, the IP will rapidly be added to global DNS Blackhole Lists (DNSBLs), resulting in the legitimate corporate email being blocked or flagged as spam by external partners.\n\n<h3>Remediation and Eradication</h3>\n<ul>\n<li><strong>Network Anomaly Detection:</strong> Monitor edge firewalls for sustained, high-volume outbound traffic on TCP port 25 (SMTP) originating from standard user endpoints rather than authorized corporate mail servers.</li>\n<li><strong>Endpoint Isolation and Sweeps:</strong> Immediately isolate the infected endpoint from the LAN to halt the spam campaign. Conduct a thorough forensic sweep to identify the Mailbot executable and remove its persistence mechanisms (registry keys and scheduled tasks).</li>\n<li><strong>IP Reputation Management:</strong> After eradication, the organization's public IP addresses must be checked against major DNSBLs (like Spamhaus). A formal delisting request must be submitted to restore legitimate email flow.</li>\n</ul>",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [
    "Trojan.Spammer.Mailbot",
    "Botnet.Mailbot",
    "Win32/Mailbot"
  ],
  "enrichment_level": "insufficient_information",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1543.003",
    "T1059",
    "T1583.003"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-07-01T17:02:47Z",
  "type": "Spam Botnet",
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}