Shellcodef

Overview

Executive Summary

Infection Vector and Technical Capabilities

• Vulnerability Exploitation: The carrier file (e.g., a PDF) contains malformed data designed to trigger a specific vulnerability (like a Buffer Overflow or Use-After-Free) in the application parsing it.
• Execution Hijacking: When the vulnerability triggers, it corrupts the application's memory space, hijacking the execution flow and forcing the CPU to execute the embedded ShellcodeF block.
• The "Stager": Shellcode must be extremely small to fit within the exploit constraints. Therefore, it typically acts as a "stager." Its sole purpose is to connect back to the attacker's server, download a larger, more fully-featured secondary payload (like a RAT, Cobalt Strike beacon, or Ransomware loader), and execute it directly in memory.

Threat Assessment

Incident Response and Remediation

• Determine Exploit Success: The most crucial step is determining if the shellcode successfully executed or if it was blocked by EDR (e.g., blocked by Exploit Guard or ASLR/DEP). Analyze EDR telemetry for unexpected child processes spawning from applications like `winword.exe` or `AcroRd32.exe`.
• Vulnerability Patching: Identify the specific application that was targeted by the exploit and ensure it, and all related software, is immediately patched to the latest vendor specifications to close the vulnerability.
• Containment and Sweeps: If execution was successful, isolate the endpoint immediately. The shellcode likely downloaded a secondary backdoor. A deep forensic sweep is required to identify and eradicate the secondary payload.

Known aliases

Threat reports may refer to this family under multiple names:

• Exploit.Shellcode
• Trojan.ShellcodeF
• Win32/Exploit

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.

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_SHELLCODEF_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Shellcodef"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "shellcodef" ascii wide nocase
        $s2 = "exploit.shellcode" ascii wide nocase
        $s3 = "trojan.shellcodef" ascii wide nocase
        $s4 = "win32/exploit" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Shellcodef (Ransomware) Execution & Triage
id: 48a5f4ad-8a18-5f30-af66-7b1528f4fa97
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Shellcodef 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/shellcodef
- 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.t1203
- attack.t1059
- attack.t1055
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_SHELLCODEF_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Shellcodef 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 = "shellcodef" 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 Shellcodef 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 Shellcodef 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 Shellcodef 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 Shellcodef 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 Shellcodef.
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 Shellcodef eradication is completely verified.

References & External Analysis

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

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Zy0Baazvyqni
• Wansrog
• Emarketing
• Exent
• Pyfiledel
• Togapy
• Emogen
• Tescrypt

Machine-readable

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