Zepto
Table of Contents
Overview
Executive Summary
Zepto is a highly destructive ransomware variant that gained massive notoriety in mid-2016. It is a direct evolution (and effectively a rebranded version) of the infamous Locky ransomware family. Zepto utilizes military-grade encryption to lock a victim's critical data, appends the `.zepto` extension to affected files, and demands a cryptocurrency ransom, causing immediate and catastrophic operational downtime.Infection Vector and Technical Capabilities
Zepto was primarily distributed through massive, automated spam campaigns orchestrated by the Necurs botnet. The phishing emails typically contained malicious `.zip` archives housing weaponized JavaScript (`.js`) or Visual Basic Script (`.vbs`) files, or `.docm` files with malicious macros. Once the script is executed, Zepto operates with devastating efficiency:- Evasion and C2 Communication: The malware often uses a Domain Generation Algorithm (DGA) to rapidly locate its command-and-control servers. It securely negotiates and receives the public RSA key required to begin the encryption process.
- Rapid File Encryption: Zepto scans local drives, removable media, and specifically targets all mapped and unmapped network shares. It encrypts files using a hybrid RSA-2048 and AES-128 algorithm, replacing the original filename and appending the `.zepto` extension.
- Shadow Copy Deletion: To prevent easy recovery, Zepto executes commands (such as `vssadmin.exe delete shadows /all /quiet`) to instantly destroy Windows Volume Shadow Copies and disable local backup routines.
- Extortion: After encryption, it drops a ransom note (often `_HELP_instructions.html` and `.bmp` files) in every affected directory and changes the desktop wallpaper to display the payment demands.
Threat Assessment
A Zepto infection is a catastrophic security incident resulting in massive data loss. Due to the strength of the RSA/AES hybrid encryption, files cannot be recovered without the private key held by the attackers or a viable offline backup.Incident Response and Remediation
- Immediate Physical Isolation: Disconnect the infected machine from the network immediately (pull the Ethernet cable/disable Wi-Fi) to halt the encryption process and prevent the ransomware from traversing SMB shares to encrypt centralized file servers.
- Do Not Reboot: Leave the machine powered on. Rebooting may trigger further destructive routines or destroy the encryption key if it temporarily resides in RAM.
- Restore from Offline Backups: The only reliable remediation is to completely wipe the infected system (bare-metal reinstall) and restore the data from secure, offline backups that were unreachable by the ransomware.
Known aliases
Threat reports may refer to this family under multiple names:
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:
- T1059.005: Restrict execution of scripting languages such as PowerShell, VBScript, or Python to authorized administrators. Enforce Script Block Logging.
- T1566.001: Scan email attachments for malicious macros, scripts, or suspicious archive files.
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-SEA | Script Execution Analysis | Detect | T1059.005 | Analyze script block syntax and command arguments at runtime to detect malicious automation. |
D3-FAED | File Alteration Early Detection | Detect | T1486 | Deploy canary files and monitor mass rename/encryption I/O spikes to terminate ransomware threads immediately. |
D3-VSS | Volume Shadow & Snapshot Hardening | Harden | T1490 | Block execution of vssadmin.exe and wmic shadowcopy delete; maintain air-gapped immutable backup repositories. |
D3-FS | File Sandboxing (Attachment Detonation) | Isolate | T1566.001 | Detonate macro-enabled documents, ISOs, and password-protected archives inside an isolated hypervisor. |
D3-DNSR | DNS Reputation Analysis | Detect | T1568.002 | Deploy recursive DNS security resolvers with algorithmic domain scoring (entropy and n-gram models) to automatically sinkhole DGA queries. |
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_ZEPTO_T1_ARTIFACT {
meta:
description = "Tier 1 Primitive Artifact: Raw string matches for Zepto"
tier = "T1 - Primitive Artifact"
confidence = "Low-Medium (Fast Triage)"
author = "SystemHelpdesk Threat Research Desk"
date = "2026-10-14"
strings:
$s1 = "zepto" ascii wide nocase
$s2 = "ransomware.zepto" ascii wide nocase
$s3 = "trojan-ransom.win32.locky.zepto" ascii wide nocase
$s4 = "filecoder.zepto" 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 - Zepto (Ransomware) Execution & Triage
id: 4e88e7db-875a-551e-9f6d-6270eb8e16bb
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
with the Zepto 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/zepto
- 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.t1486
- attack.t1490
- attack.t1566_001
- attack.t1059_005
- attack.t1568_002
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: criticalTier 3 Attribution Fingerprint Rule (High Fidelity)
Deep signature matching distinctive operational fingerprints and payload characteristics.
rule MALWARE_WIN_ZEPTO_T3_ATTRIBUTION {
meta:
description = "Tier 3 Attribution Fingerprint: Heuristic detection for Zepto 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 = "zepto" 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.
- Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Zepto from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.
- Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Zepto symmetric encryption keys or uncompiled payload components may still reside in memory.
- 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 Zepto to inhibit recovery.
- 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.
- Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Zepto 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.
- Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Zepto.
- Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.
- Do not connect clean backup drives or external storage to the affected network until Zepto eradication is completely verified.
References & External Analysis
- Search "zepto" on VirusTotal (External Analysis)
- Search "zepto" on Any.Run (Sandbox Sandbox)
- Search "zepto" on MalwareBazaar (Malware Samples)
Frequently Asked Questions
What is Zepto and what threat category does it belong to?
Zepto 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.
How does Zepto establish persistence and evade defensive controls?
Zepto 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.
What are the essential incident response steps for mitigating a Zepto compromise?
Security teams responding to Zepto 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.
What cryptographic algorithms and file targeting techniques does Ransomware.Zepto employ during execution?
Ransomware.Zepto 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.
Are decryptors available for Ransomware.Zepto, and what is the recommended recovery procedure?
Decryption availability for Ransomware.Zepto 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.
How do I remove the Zepto Ransomware from Windows?
Manual removal of Zepto 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 Zepto a virus or a Ransomware?
Zepto is classified as a Ransomware. Unlike traditional viruses that infect files, modern malware like Zepto typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Zepto infection?
Symptoms of Zepto 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 Ransomwares
Want to prevent Zepto and similar threats from compromising your organization? Read our comprehensive defensive guide: Ransomware Containment & Incident Response.
📣 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/zepto.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.