{
  "family": "fsysna",
  "sample_count": 427,
  "category": "trojan_generic",
  "description": "Trojan:Win32/Fsysna is a persistent, heavily obfuscated trojan downloader designed to breach endpoint defenses and securely deliver secondary payloads, often prioritizing banking trojans or ransomware.<br><br><b>Understanding Fsysna</b><br>To an end-user, an Fsysna infection is typically invisible until the secondary payload executes. For threat intelligence analysts, Fsysna is a highly capable staging mechanism. It is engineered to evade initial static detection through complex packing routines. Its primary function is to profile the infected system and reach out to a Command-and-Control (C2) server to retrieve the final, destructive payload.<br><br><b>Execution and Evasion Strategies</b><br>Fsysna is commonly distributed via massive malspam campaigns containing weaponized attachments (like ZIP files or Office macros) or through exploit kits. Upon execution, it drops a randomized executable into the <code>%Temp%</code> directory. It establishes persistence by creating a hidden scheduled task or modifying the Registry Run keys. To hide its network activity, Fsysna frequently injects its core downloading routine into legitimate system processes (like <code>svchost.exe</code> or <code>explorer.exe</code>). The C2 communications are often encrypted and sent over non-standard ports.<br><br><b>Indicators of Compromise (IoCs)</b><br>Threat hunters should investigate EDR alerts for 'Suspicious Process Injection' or the rapid creation of highly entropic files in user directories. Network logs will often reveal Fsysna reaching out to compromised domains or IP addresses associated with known cybercrime infrastructure. The presence of unexpected, hidden scheduled tasks designed to execute randomly named binaries is a strong IoC. Memory analysis is necessary to extract the injected downloader module.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1105",
    "T1027.002",
    "T1189",
    "T1053.005",
    "T1055"
  ],
  "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": "T1053.005",
      "name": "Scheduled Task/Job: Scheduled Task",
      "tactic": "Persistence"
    },
    {
      "id": "T1027.002",
      "name": "Obfuscated Files or Information: Software Packing",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1189",
      "name": "Drive-by Compromise",
      "tactic": "Initial Access"
    }
  ],
  "containment_steps": [
    "Isolate the endpoint from the network immediately to prevent Fsysna from successfully downloading and executing its secondary payloads.",
    "Audit the Windows Task Scheduler and Registry Run keys to identify and remove the Fsysna persistence mechanisms.",
    "Review firewall and proxy logs to identify the C2 domains Fsysna attempted to contact, and block them enterprise-wide.",
    "Perform a full memory and disk scan with a reputable EDR solution to eradicate the dropped executables and injected processes."
  ],
  "what_to_avoid": [
    "Do not close an incident simply because the initial Fsysna dropper was quarantined; always verify if secondary payloads were downloaded.",
    "Avoid relying solely on manual file deletion, as the injected processes will likely just recreate the dropped binaries."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}