Psshell

Overview

Executive Summary

Infection Vector and Technical Capabilities

• Fileless Execution: PSShells are often executed entirely in memory using "Download Cradles" (e.g., `Invoke-Expression (New-Object Net.WebClient).DownloadString(...)`). This allows the attacker to establish a reverse shell without ever writing a `.ps1` script file to the hard drive, evading many traditional antivirus scanners.
• AMSI Evasion: Modern PSShell frameworks incorporate code specifically designed to hook and bypass the Windows Anti-Malware Scan Interface (AMSI), preventing Windows Defender from scanning the malicious PowerShell commands as they are executed.
• Post-Exploitation Framework: Once the shell is established, the attacker has unrestricted command-line access to the system. They can utilize built-in PowerShell cmdlets to dump credentials (e.g., Mimikatz modules), enumerate Active Directory, and pivot to other systems on the network.

Threat Assessment

Incident Response and Remediation

• Behavioral Monitoring (EDR and Script Block Logging): Detection relies heavily on EDR telemetry and Windows Event Log 4104 (Script Block Logging). Analysts must review these logs to reconstruct the commands executed by the attacker during the PSShell session.
• Immediate Network Isolation: The endpoint must be isolated instantly to severe the reverse shell connection and halt the attacker's lateral movement.
• Total Re-imaging: Because the attacker had interactive command-line access, they could have established deep, secondary persistence mechanisms (like WMI event subscriptions or modified registry keys) that are difficult to uncover. A complete bare-metal wipe and re-image is required, alongside a global password reset.

Known aliases

Threat reports may refer to this family under multiple names:

• HackTool.PSShell
• Riskware.PowerShell
• Trojan.PowerShell.ReverseShell
• Nishang

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1059: Restrict execution of scripting languages such as PowerShell, VBScript, or Python to authorized administrators. Enforce Script Block Logging.
• 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.

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

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:

rule MALWARE_WIN_PSSHELL_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Psshell"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "psshell" ascii wide nocase
        $s2 = "hacktool.psshell" ascii wide nocase
        $s3 = "riskware.powershell" ascii wide nocase
        $s4 = "trojan.powershell.reverseshell" ascii wide nocase
        $s5 = "nishang" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Psshell (Ransomware) Execution & Triage
id: d2a00928-3586-55ac-9b43-360d9028b6be
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Psshell malware family. Detects volume shadow copy deletion, boot status
  tampering, and recovery inhibition characteristic of modern ransomware operations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/psshell
- 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.ransomware
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_001
- attack.t1059
- attack.t1562_001
- attack.t1071_001
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \vssadmin.exe
    - \wmic.exe
    - \wbadmin.exe
    - \bcdedit.exe
    CommandLine|contains:
    - delete shadows
    - shadowcopy delete
    - resize shadowstorage
    - recoveryenabled no
    - ignoreallfailures
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: critical

rule MALWARE_WIN_PSSHELL_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Psshell 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 = "psshell" 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
}

Containment & Response Steps

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

1. Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Psshell from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.
2. Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Psshell symmetric encryption keys or uncompiled payload components may still reside in memory.
3. Audit process execution logs and terminate active scripting interpreters (e.g. PowerShell, CMD, WScript) or commands executing 'vssadmin.exe delete shadows' or 'wbadmin' used by Psshell to inhibit recovery.
4. Investigate the initial compromise vector (such as exposed RDP instances, spearphishing attachments, or vulnerable edge gateways) and enforce an immediate credential reset for all compromised Active Directory accounts.
5. Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Psshell binary and related persistence hooks are eradicated.

What to Avoid

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

1. Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Psshell.
2. Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.
3. Do not connect clean backup drives or external storage to the affected network until Psshell eradication is completely verified.

References & External Analysis

• Search "psshell" on VirusTotal (External Analysis)
• Search "psshell" on Any.Run (Sandbox Sandbox)
• Search "psshell" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Tosthin
• Skillis
• Bandit
• Rogan
• Pshell
• Stocde
• Patchload
• Ruskill

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/psshell.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.