Psdownload

Overview

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.

Understanding Psdownload
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.

Execution and Evasion Strategies
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.

Indicators of Compromise & Impact
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.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

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.
• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
• T1566.001: Scan email attachments for malicious macros, scripts, or suspicious archive files.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_PSDOWNLOAD {
    meta:
        description = "Detects Psdownload (ransomware)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "psdownload" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Psdownload Activity
id: cc58eaf56a92946534f4819b56e45bc7
status: experimental
description: Detects generic indicators of the psdownload malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*psdownload*"
    condition: selection
level: medium

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Isolate the endpoint immediately; if the Psdownload script executed successfully, a severe secondary payload (like Cobalt Strike) is actively running in memory.
2. Do NOT reboot the machine immediately; capture a full forensic memory image to extract the payload that was executed reflectively in RAM.
3. Extract and decode the obfuscated PowerShell command line from EDR telemetry or Windows Event Logs (ID 4104) to identify the C2 domain.
4. Review firewall and proxy logs to identify what data, if any, the secondary payload has already exfiltrated.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not assume the threat is contained just because the initial Word document was deleted; the payload is running independently in memory.
2. Avoid disabling PowerShell Script Block Logging in the enterprise environment; it is the only reliable way to analyze these fileless attacks.

References & External Analysis

• Search "psdownload" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Shufab
• Cognosads
• Vakcune
• Msposer
• Netthief

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/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.