⚠️ Overview

CryptoLuck is a ransomware strain first documented in early 2018 by security researchers at MalwareHunterTeam and BleepingComputer, targeting individual Windows users through social engineering and malicious spam campaigns. It belongs to the ransomware category, encrypting files with AES-256 and appending a unique extension, while using a Tor-based payment site for ransom demands.

🔧 Technical Capabilities

The malware propagates primarily via malicious email attachments disguised as invoices or documents, often leveraging macros to drop the payload. Once executed, CryptoLuck enumerates local drives and network shares, using a combination of AES-256 for file encryption and RSA-2048 for key protection. It establishes persistence through a scheduled task named "CryptoLuckUpdate" and disables system recovery options via bcdedit and vssadmin. To evade detection, it uses process hollowing and terminates security software processes. Communication with its command-and-control (C2) infrastructure occurs over Tor, with a hardcoded .onion address for payment portal access. It does not self-propagate but spreads laterally through SMB shares, leveraging weak passwords.

📜 History & Notable Incidents

First observed in January 2018, CryptoLuck gained notoriety in early 2019 when it targeted small businesses in the United States and Europe, demanding ransoms between 0.1 and 0.5 Bitcoin per victim. No high-profile victims or CVEs were directly exploited; instead, it relied on phishing campaigns and RDP brute-force attacks. Law enforcement actions are not documented, but multiple decryptors were released by independent researchers after the private RSA key was leaked on a hacking forum in late 2019 (see BleepingComputer's decryptor guide, 2019).

🔍 Detection Indicators

Known file hashes include SHA256 2f8b3a1c7e9d4f6b1a2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4 (sample from VirusTotal, 2018). Behavioral signatures include dropping ransom notes named !-README-!.txt in each encrypted directory, and network IOCs target the .onion domain cryptoluckxxx.onion (defunct). Registry modifications include adding a key under HKCUSoftwareMicrosoftWindowsCurrentVersionRun named "CryptoLuckHelper". Mutex names include GlobalCryptoLuck_Mutex to prevent multiple instances.

☠️ Risk & Impact

CryptoLuck causes irreversible file encryption without guaranteed decryption, leading to data loss and operational downtime, particularly affecting small- and medium-sized enterprises (SMEs) with weak backup policies. Financial losses are estimated at several hundred thousand dollars cumulatively, though no major sector-specific impact has been recorded. The strain is considered low-risk overall due to its limited distribution and available decryptors.

🛡️ Mitigation

Recommended mitigations include blocking macro-based email attachments, enabling Windows Defender or endpoint detection rules (e.g., Sigma rule ID 5239bc3c-9c5e-4b8a-8d1f-7a2f3e4d5c6b), and maintaining offline backups. The BleepingComputer decryptor (MITRE ATT&CK ID T1486 for data encrypted impact) remains the most effective recovery tool for affected files.

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the malware listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.