{
  "family": "psdownload",
  "sample_count": 41,
  "category": "ransomware",
  "description": "TrojanDownloader:PowerShell/Psdownload is a behavioral heuristic detection utilized by security software to identify malicious PowerShell scripts designed specifically to act as 'downloaders'. These scripts are engineered to reach out to the internet, retrieve a secondary, high-severity payload (like ransomware, Cobalt Strike, or a RAT), and execute it directly in memory, often completely bypassing disk-based antivirus scanning.<br><br><b>Understanding Psdownload</b><br>To the end-user, the infection often begins with enabling macros in a Word document, which briefly flashes a blue command window before disappearing. For a security analyst, a 'Psdownload' alert signifies a 'Fileless' or 'Living off the Land' (LotL) attack. The attacker is abusing legitimate Windows administration tools (`powershell.exe`) to execute their malicious logic, making detection difficult because the primary executable is trusted by the operating system.<br><br><b>Execution and Evasion Strategies</b><br>The infection vector is almost always a spearphishing email with a weaponized Office document. When the user enables macros, VBA code spawns a hidden `powershell.exe` process (`T1059.001`). The script passed to PowerShell is usually heavily obfuscated (using Base64 encoding or string manipulation) to bypass static analysis (`T1027`). The core logic of the script utilizes cmdlets like `Invoke-WebRequest` or `System.Net.WebClient.DownloadString` to fetch the payload from a C2 server. The most dangerous variants use `Invoke-Expression` (IEX) or reflective DLL injection to execute the downloaded payload entirely within the RAM allocated to the PowerShell process, leaving zero forensic trace on the hard drive.<br><br><b>Indicators of Compromise & Impact</b><br>The impact depends entirely on the payload the PowerShell script successfully executed. EDR platforms and PowerShell Script Block Logging (Event ID 4104) are critical for detection. EDR will flag `powershell.exe` spawning with suspicious execution policies (`-ExecutionPolicy Bypass -WindowStyle Hidden -EncodedCommand`). Network logs will reveal the PowerShell process making anomalous outbound HTTP/HTTPS connections. Analysts must decode the logged script blocks to determine the C2 URL and the nature of the downloaded payload.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1027",
    "T1105",
    "T1059.001",
    "T1566.001",
    "T1620"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1059.001",
      "name": "Command and Scripting Interpreter: PowerShell",
      "tactic": "Execution"
    },
    {
      "id": "T1105",
      "name": "Ingress Tool Transfer",
      "tactic": "Command and Control"
    },
    {
      "id": "T1027",
      "name": "Obfuscated Files or Information",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1620",
      "name": "Reflective Code Loading",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1566.001",
      "name": "Phishing: Spearphishing Attachment",
      "tactic": "Initial Access"
    }
  ],
  "containment_steps": [
    "Isolate the endpoint immediately; if the Psdownload script executed successfully, a severe secondary payload (like Cobalt Strike) is actively running in memory.",
    "Do NOT reboot the machine immediately; capture a full forensic memory image to extract the payload that was executed reflectively in RAM.",
    "Extract and decode the obfuscated PowerShell command line from EDR telemetry or Windows Event Logs (ID 4104) to identify the C2 domain.",
    "Review firewall and proxy logs to identify what data, if any, the secondary payload has already exfiltrated."
  ],
  "what_to_avoid": [
    "Do not assume the threat is contained just because the initial Word document was deleted; the payload is running independently in memory.",
    "Avoid disabling PowerShell Script Block Logging in the enterprise environment; it is the only reliable way to analyze these fileless attacks."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}