{ "family": "pshell", "sample_count": 3, "category": "ransomware", "description": "Trojan:PowerShell/Pshell is not a specific malware family, but a highly critical **Generic Heuristic Detection** focused entirely on the malicious abuse of the Windows PowerShell framework. Microsoft Defender and other AV engines use this classification when they detect a PowerShell script or command-line execution exhibiting behaviors that strongly indicate malicious intent, regardless of the specific payload being delivered.

Understanding Pshell (Living off the Land)
To an end-user, this detection usually appears as a blocked script execution in the background. For a security analyst, Pshell is a massive red flag indicating an attack utilizing 'Living off the Land' (LotL) techniques. By abusing PowerShell (`T1059.001`), attackers leverage a trusted, built-in system administration tool to download payloads, execute code in memory, and bypass traditional application whitelisting and file-based antivirus scanners.

Execution and Evasion Mechanics
The specific mechanics triggering a Pshell alert are vast. Common triggers include: obfuscated or heavily encoded PowerShell scripts (e.g., using Base64 encoding via the `-enc` or `-EncodedCommand` flags) (`T1027`); scripts that attempt to use `Invoke-WebRequest` or `Net.WebClient` to download executables directly into memory (fileless malware) (`T1105`); scripts attempting to bypass the Execution Policy (`-ExecutionPolicy Bypass`); or scripts containing known malicious cmdlets like `Invoke-ReflectivePEInjection` (often associated with tools like Empire or PowerSploit).

Indicators of Compromise & Impact
The impact depends entirely on what the PowerShell script was attempting to execute (ranging from a simple coinminer to a devastating ransomware deployment). Host-based IoCs are centered around the PowerShell operational event logs (Event IDs 4104, 4103) which must be analyzed to decode the obfuscated command that triggered the AV block. Network IoCs include the PowerShell process (`powershell.exe`) making anomalous outbound connections to download secondary payloads.", "cta": "Published by the SystemHelpdesk team.", "aliases": [], "enrichment_level": "expert-seo", "faq": [ { "@type": "Question", "name": "What is Pshell and what threat category does it belong to?", "acceptedAnswer": { "@type": "Answer", "text": "Pshell is classified as a Ransomware. Documented across security telemetry, it is engineered to execute unauthorized operations, establish persistent footholds on target endpoints, and facilitate malicious campaigns targeting enterprise and individual environments." } }, { "@type": "Question", "name": "How does Pshell establish persistence and evade defensive controls?", "acceptedAnswer": { "@type": "Answer", "text": "Pshell typically establishes persistence through registry run keys, scheduled tasks, or service installations, while evading signature-based antivirus solutions through code obfuscation, memory injection, or anti-analysis sandbox checks." } }, { "@type": "Question", "name": "What are the essential incident response steps for mitigating a Pshell compromise?", "acceptedAnswer": { "@type": "Answer", "text": "Security teams responding to Pshell should immediately isolate affected endpoints from the network, perform memory triage to capture volatile forensic artifacts, audit registry and startup persistence mechanisms, revoke exposed user credentials, and restore systems from verified, clean backups." } }, { "@type": "Question", "name": "What cryptographic algorithms and file targeting techniques does Pshell employ during execution?", "acceptedAnswer": { "@type": "Answer", "text": "Pshell typically leverages hybrid cryptographic architectures combining symmetric stream or block ciphers (such as AES-256 or ChaCha20) for rapid file encryption with asymmetric algorithms (such as RSA-2048 or Curve25519) to securely protect the session keys. It aggressively targets sensitive file extensions including corporate documents, databases, virtual disks, and backups while systematically executing commands to delete Volume Shadow Copies (vssadmin delete shadows /all /quiet) and disable system recovery options." } }, { "@type": "Question", "name": "Are decryptors available for Pshell, and what is the recommended recovery procedure?", "acceptedAnswer": { "@type": "Answer", "text": "Decryption availability for Pshell depends on whether security researchers or law enforcement (such as the No More Ransom initiative) have recovered the master private keys or discovered flaws in its key generation routines. Victims should never pay the extortion demand, as payment fuels criminal operations without guaranteeing file restoration. The recommended recovery procedure entails isolating infected hosts, conducting forensic disk imaging, identifying the root access vector, and restoring validated systems from immutable offline backups." } } ], "faq_count": 5, "mitre_attack": [ "T1059.001", "T1105", "T1027" ], "cisa_advisory": null, "last_updated": "2026-06-09", "mitre_attack_detail": [ { "id": "T1059.001", "name": "Command and Scripting Interpreter: PowerShell (The core heuristic trigger)", "tactic": "Execution" }, { "id": "T1027", "name": "Obfuscated Files or Information (Encoded commands)", "tactic": "Defense Evasion" }, { "id": "T1105", "name": "Ingress Tool Transfer (Downloading payloads via PS)", "tactic": "Command and Control" } ], "containment_steps": [ "Immediately review the Windows Event Logs (specifically PowerShell Operational logs, Event ID 4104 'Script Block Logging') to capture and decode the exact script that executed.", "Isolate the endpoint if the decoded script indicates a successful payload execution (e.g., it dropped a file or established a reverse shell) before the AV could block it.", "Analyze the decoded script to identify C2 domains or IP addresses and block them at the network perimeter.", "Ensure PowerShell Constrained Language Mode is enforced and Script Block Logging is enabled across the enterprise." ], "what_to_avoid": [ "Do not ignore the alert assuming it is a benign admin script; heavily encoded or web-downloading PowerShell commands are rarely legitimate administrative tasks.", "Avoid relying solely on file-based AV logs; you must investigate the PowerShell command line arguments and script blocks to understand the attack." ], "target_industries": [ "Healthcare", "Critical Infrastructure", "Enterprise" ], "motivation": "Financial Extortion", "threat_actors": [ "Unknown / Cybercriminal" ], "target_geographies": [ "Global" ], "attack_stage": [ "defense_evasion", "impact" ], "ecosystem": [ "windows_pe" ], "is_emerging": false, "target_platforms": [ "Windows 11", "Windows 10", "Windows Server 2022", "Windows Server 2019" ] }