Psdownload
Table of Contents
Overview
Psdownload (tracked across cybersecurity vendors and endpoint detection platforms under signatures such as TrojanDownloader:PowerShell/Psdownload, Trojan:PowerShell/Psdownload.A, and Trojan:PowerShell/Psdownload!MSR) represents a prolific family of weaponized PowerShell scripts and living-off-the-land (LotL) downloaders active since 2017. Designed to achieve fileless execution or stage secondary malware payloads onto Windows endpoints, Psdownload scripts are typically delivered via phishing emails with macro-enabled Office documents, weaponized ISO/LNK shortcuts, or malvertising redirection chains. Upon execution, the obfuscated PowerShell script executes with execution bypass flags (-ExecutionPolicy Bypass -NoProfile -WindowStyle Hidden), invokes WebClient or Invoke-WebRequest APIs (such as Net.WebClient.DownloadFile or Invoke-RestMethod), and dynamically retrieves encoded secondary payloads—including Cobalt Strike beacons, banking trojans, and ransomware—saving or executing them directly in system memory using AMSI bypass techniques.
Known aliases
Threat reports may refer to this family under multiple names:
Family Pedigree & Lineage
Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:
Known Derivatives & Downstream Variants: Trojandownloader:Powershell/Psdownload.A · Trojandownloader:Powershell/Psdownload.B
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1059.001 · T1105 · T1562.001 · T1027.010 · T1071.001
Tactical Mitigations
Based on the techniques used by this family, consider the following defensive strategies:
- T1059.001: Restrict execution of PowerShell. Enforce PowerShell Constrained Language Mode and Script Block Logging.
- T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.
- T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
MITRE D3FEND™ Defensive Countermeasures
Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):
| D3FEND ID | Countermeasure Name | Tactic | Countered ATT&CK | Defensive Guidance |
|---|---|---|---|---|
D3-BDA | Binary De-obfuscation & Unpacking | Analyze | T1027.010 | Utilize memory dump scanners and entropy inspection to unpack encrypted stagers during process creation. |
D3-PSBL | PowerShell Script Block Logging | Detect | T1059.001 | Enable PowerShell event ID 4104 and Constrained Language Mode to neuter obfuscated script payloads. |
D3-WAF | Web Content Filtering & Inspection | Filter | T1071.001 | Block newly registered domains (NRDs) and inspect HTTP Host and URI headers for known C2 profiles. |
D3-NTI | Network Traffic Inspection | Detect | T1105 | Inspect deep packet payloads for anomalous staging binaries and unauthorized egress protocols. |
D3-STA | Security Tool Anti-Tamper Enforcement | Harden | T1562.001 | Block unauthorized modification of antivirus registry flags and prevent stopping security agent services. |
Tiered Detection Rules (Cisco CAIRN Model)
Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:
Tier 1 Primitive Artifact Rule (Fast Triage)
Matches raw strings and file markers. Vulnerable to binary repacking and simple obfuscation.
rule MALWARE_WIN_PSDOWNLOAD_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Psdownload"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "psdownload" ascii wide nocase
$s2 = "trojandownloader:powershell/psdownload" ascii wide nocase
$s3 = "trojan:powershell/psdownload.a" ascii wide nocase
$s4 = "trojandownloader:powershell/psdownload.b" ascii wide nocase
$s5 = "powershell/downloader.psdownload" ascii wide nocase
$s6 = "trojan:powershell/psdownload!msr" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Tier 2 Behavioral Context Rule (Process Chains & Sigma)
Tracks parent-child process anomalies and suspicious scripting telemetry. Resilient against file renames.
title: SystemHelpDesk Detection - Psdownload (Trojan Downloader) Execution & Triage
id: 2b00dacf-7921-5481-8fa4-91291d7e30ab
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Psdownload malware family. Detects suspicious execution from temporary
user directories with hidden window flags and background transfer utilities.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/psdownload
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.trojan-downloader
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_001
- attack.t1105
- attack.t1562_001
- attack.t1027_010
- attack.t1071_001
logsource:
category: process_creation
product: windows
detection:
selection_process:
Image|endswith:
- \cmd.exe
- \powershell.exe
- \cscript.exe
- \wscript.exe
CommandLine|contains:
- AppData\Local\Temp
- -WindowStyle Hidden
- /e:jscript
- bitsadmin /transfer
condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: mediumTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_PSDOWNLOAD_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Psdownload tradecraft"
tier = "T3 - Attribution Fingerprint"
confidence = "High (Confirmed Family Signature)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
// Core family identifier & heuristic payload signatures
$attrib_str = "psdownload" ascii wide nocase
$pe_magic = "MZ" ascii
$net_marker = "http" ascii nocase
condition:
uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}References & External Analysis
Frequently Asked Questions
What is TrojanDownloader:PowerShell/Psdownload?
Psdownload is a family of malicious PowerShell downloaders that abuse legitimate Windows management utilities to download and execute secondary malware payloads.
How does Psdownload evade PowerShell execution policy restrictions?
Attackers launch the PowerShell process with the '-ExecutionPolicy Bypass' and '-NoProfile' flags, allowing unsigned malicious scripts to run unrestricted.
What payloads are typically delivered by Psdownload?
Threat actors use Psdownload to deploy Cobalt Strike beacons, remote access trojans (RATs), cryptocurrency miners, and ransomware.
How does Psdownload bypass the Antimalware Scan Interface (AMSI)?
It uses in-memory memory patching techniques to overwrite the AmsiScanBuffer function in amsi.dll, preventing Windows Defender from inspecting script contents.
What defensive configurations protect against PowerShell downloaders?
Enable PowerShell Constrained Language Mode, enforce Script Block Logging (Event ID 4104), and deploy attack surface reduction (ASR) rules to block obfuscated scripts.
How do I remove the Psdownload Trojan_Downloader from Windows?
Manual removal of Psdownload is highly discouraged as it may leave persistence mechanisms intact. We recommend disconnecting the device from the internet and utilizing a professional incident response service or enterprise-grade EDR software to conduct a full forensic sweep.
Is Psdownload a virus or a Trojan_Downloader?
Psdownload is classified as a Trojan_Downloader. Unlike traditional viruses that infect files, modern malware like Psdownload typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Psdownload infection?
Symptoms of Psdownload can include unexpected system slowness, unauthorized outbound network traffic to unknown IP addresses, disabled security software, and suspicious background processes running from AppData or Temp directories.
Protect Your Network Against Trojan_Downloaders
Want to prevent Psdownload and similar threats from compromising your organization? Read our comprehensive defensive guide: Banking Trojan Protection for Businesses.
📣 Threat Intel Correction or Update?
Notice an outdated IOC, unlisted alias, or disputed attribution? Threat researchers are invited to propose an update on GitHub or contact the SystemHelpDesk research desk. All community revisions are credited in our public CHANGELOG.
Machine-readable
Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/psdownload.json
Ecosystem & Interactive Environments
This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.