{
  "family": "ursu",
  "sample_count": 1168,
  "category": "trojan_generic",
  "description": "Trojan:Win32/Ursu is an evasive, generic trojan dropper characterized by its rapid polymorphism and use in targeted, fast-moving malware campaigns.<br><br><b>What is Ursu?</b><br>For general users, Ursu provides no visual indication of infection. For threat hunters and SOC analysts, Ursu is recognized as a 'first-stage' dropper. Its primary goal is not to steal data itself, but to breach the endpoint's defenses, establish a silent foothold, profile the system's security software, and download the final, destructive payload (such as a remote access trojan or ransomware).<br><br><b>Infection Vectors & Threat Hunting</b><br>Ursu is heavily utilized in massive spam campaigns, often disguised as shipping invoices, tax documents, or legal notices containing weaponized macros or malicious JavaScript attachments. Upon execution, the dropper rapidly unpacks itself in memory. It uses anti-analysis techniques, checking for the presence of sandboxes, debuggers, or specific EDR agents. If the coast is clear, it injects into a legitimate process (like <code>svchost.exe</code>) and connects to a hardcoded list of compromised domains to download the secondary payload.<br><br><b>Forensic Analysis & Impact</b><br>The impact of Ursu is entirely dependent on the secondary payload it fetches. Threat hunters should investigate EDR alerts for 'Suspicious Process Injection' or 'Office Application Spawning Command Prompt'. Network logs will often reveal Ursu reaching out to newly registered domains or compromised WordPress sites via HTTPS to fetch encrypted binary blobs. Dropped files in the <code>%Temp%</code> directory exhibiting high entropy (packed data) are strong indicators of an Ursu infection.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1497.001",
    "T1566.001",
    "T1105",
    "T1055",
    "T1204.002"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1105",
      "name": "Ingress Tool Transfer",
      "tactic": "Command and Control"
    },
    {
      "id": "T1055",
      "name": "Process Injection",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1497.001",
      "name": "Virtualization/Sandbox Evasion: System Checks",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1566.001",
      "name": "Phishing: Spearphishing Attachment",
      "tactic": "Initial Access"
    },
    {
      "id": "T1204.002",
      "name": "User Execution: Malicious File",
      "tactic": "Execution"
    }
  ],
  "containment_steps": [
    "Immediately isolate the endpoint to prevent Ursu from successfully downloading the secondary, destructive payload.",
    "Review firewall and DNS logs to identify the C2 domains Ursu attempted to contact, and block them proactively across the network.",
    "Perform a deep forensic scan to determine if the secondary payload was successfully executed before the endpoint was isolated.",
    "Force a password reset if the secondary payload is suspected to be an information stealer."
  ],
  "what_to_avoid": [
    "Do not assume the threat is neutralized simply by deleting the initial phishing email or attachment; the memory-resident dropper may already be active.",
    "Avoid uploading the Ursu payload to public sandboxes (like VirusTotal) if it was used in a targeted attack, as this tips off the attacker."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}