Cryptolocker

Overview

CryptoLocker is the historic archetype of modern asymmetric ransomware, first discovered in September 2013. Engineered and operated under the criminal syndicate led by Russian national Evgeniy Mikhailovich Bogachev (known online as 'lucky12345' and 'slavik'), CryptoLocker pioneered the ruthless pairing of AES-256 local file encryption with an asymmetric RSA-2048 public-key infrastructure, ensuring that victim files could not be decrypted without the private key held exclusively on attacker-controlled command servers. CryptoLocker was primarily distributed via Bogachev's GameOver Zeus botnet and high-volume phishing emails carrying malicious attachments. In May and June 2014, an unprecedented multinational law enforcement coalition led by the US Department of Justice, the FBI, Europol EC3, the UK National Crime Agency (NCA), and police agencies across 10 nations executed 'Operation Tovar'. The operation seized the central command-and-control servers, dismantled GameOver Zeus, and recovered the master database of private decryption keys. The US DOJ indicted Bogachev in the Western District of Pennsylvania, and the FBI placed him on the Cyber's Most Wanted list with a record $3 million reward. Following the takedown, security firms FireEye and Fox-IT launched the free 'DecryptCryptoLocker' portal, enabling hundreds of thousands of victims worldwide to recover their data without paying ransom.

Known aliases

Threat reports may refer to this family under multiple names:

• CryptoLocker
• Trojan.CryptoLocker
• Win32/CryptoLocker
• Ransom.CryptoLocker

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• Evgeniy Mikhailovich Bogachev ('slavik') / Operation Tovar Coalition (DOJ / FBI / Europol) High confidence
  Basis: Federal indictment unsealed in the Western District of Pennsylvania against Evgeniy Bogachev in June 2014 following Operation Tovar, which dismantled the GameOver Zeus and CryptoLocker command infrastructure and recovered master decryption keys. [source]

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Derived From / Upstream Ancestry: Gameover Zeus

Known Derivatives & Downstream Variants: Cryptolocker Original (2013) · Cryptolocker V2 Clone · Operation Tovar Master Key Recovery

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:

• 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):

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2013-3906 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Command & Control (C2) and Network Profile

How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• 2efb6d17b5e4c6981cfda552553ca4be969796ff07a835a96aef71a2ec703ce5
• b1b4c330f89fa6d165f973e20e8b22a08846c4f09a5b3a8634860b0ec89c565d

Delivery vectors

• GameOver Zeus peer-to-peer botnet secondary payload drops
• Phishing campaigns spoofing FedEx, UPS, or banking notifications containing weaponized ZIP files with double-extension executables

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run entry pointing to staged executable in %APPDATA%
• Storage of encryption keys and list of encrypted file paths in registry subkeys under HKCU\Software\CryptoLocker

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_CRYPTOLOCKER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Cryptolocker"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "cryptolocker" ascii wide nocase
        $s2 = "cryptolocker" ascii wide nocase
        $s3 = "trojan.cryptolocker" ascii wide nocase
        $s4 = "win32/cryptolocker" ascii wide nocase
        $s5 = "ransom.cryptolocker" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Cryptolocker (Ransomware) Execution & Triage
id: b94945a6-88a1-52f6-9b34-6f81336c36e5
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Cryptolocker 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/cryptolocker
- 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.t1071_001
- attack.t1568_002
- attack.t1547_001
- attack.t1027
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_CRYPTOLOCKER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Cryptolocker 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 = "cryptolocker" 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 Cryptolocker 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 Cryptolocker 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 Cryptolocker 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 Cryptolocker 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 Cryptolocker.
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 Cryptolocker eradication is completely verified.

References & External Analysis

• US DOJ Press Release - Global Effort Disrupts GameOver Zeus and CryptoLocker
• FBI Most Wanted - Evgeniy Mikhailovich Bogachev
• MITRE ATT&CK - CryptoLocker
• Search "cryptolocker" on VirusTotal (External Analysis)
• Search "cryptolocker" on Any.Run (Sandbox Sandbox)
• Search "cryptolocker" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Canbis
• Crypton
• Nlbrute
• Mailpassview
• Wdjiange
• Nagoot
• Alreay
• Patpoopy

Machine-readable

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