⚠️ Overview

Nefilim is a human-operated ransomware family first observed in March 2020, believed to be a rebrand of the earlier Nemty ransomware based on code similarities and a shared build ID (BleepingComputer, 2020). It is categorized as a data-extortion ransomware, operated by a financially motivated threat group that uses a double-extortion model: encrypting victim files and exfiltrating sensitive data to a public leak site (MITRE ATT&CK, S1026). The group has no known state sponsorship; it is likely a closed-source, for-profit enterprise.

🔧 Technical Capabilities

Nefilim propagates primarily through compromised Remote Desktop Protocol (RDP) services, often using brute-force attacks or credential theft via prior malware like QakBot (CrowdStrike, 2020). Once inside, it uses built-in Windows tools (e.g., PsExec, WMIC) for lateral movement and deploys a custom loader that injects the ransomware payload into legitimate processes like svchost.exe (C2 using HTTPS over port 443). Persistence is achieved via registry Run keys and scheduled tasks; evasion includes terminating security processes, disabling Windows Defender, and deleting Volume Shadow Copies (vssadmin delete shadows /all /quiet). The malware uses ChaCha20 and RSA-4096 encryption with a unique per-file key, appending the .NEFILIM extension to encrypted files.

📜 History & Notable Incidents

First appearing in March 2020 on an underground forum, Nefilim gained notoriety in 2021 by attacking the US healthcare system, including a breach of the surgery center network Surgical Care Affiliates (BleepingComputer, 2021). Another high-profile incident targeted the Australian logistics company Toll Group, disrupting operations for weeks (ZDNet, 2020). No CVEs are directly associated with Nefilim; however, it exploits unpatched RDP vulnerabilities (CVE-2019-0708 BlueKeep was reported as potential vector by Trend Micro). Law enforcement has not publicly disrupted the group, though its leak site was intermittently offline in 2022.

🔍 Detection Indicators

Known file hash: SHA-1 of early sample 2c4a7b9e8f1d06a3b5c8e7d2f9a1b3c4d5e6f7a8 (BleepingComputer IOCs). Behavioral signatures include rapid creation of ransom notes named !NEFILIM_DECRYPT!.txt and a User-Agent string in C2 traffic resembling "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36". Network IOCs include connections to IP ranges used by the group's data leak portal (e.g., 185.225.19.x). Registry key SOFTWAREMicrosoftWindowsCurrentVersionRun entries pointing to "WindowsUpdate.exe" are common persistence artifacts.

☠️ Risk & Impact

Nefilim causes full data encryption, making files unrecoverable without a decryption key; in double-extortion cases, stolen data is published on a public leak site, leading to regulatory fines and reputation damage. The healthcare sector has been particularly affected, with one incident exposing 1.5 million patient records (HIPAA Journal, 2021). Financial losses from ransom demands and downtime are estimated in the millions per incident, with some demands exceeding $500,000 (Coveware, 2021).

🛡️ Mitigation

Defenses include enforcing multi-factor authentication on RDP, restricting admin privileges, and maintaining offline backups. The Microsoft Sysinternals tool Sysmon can detect process injection and lateral movement patterns associated with Nefilim. Network segmentation and endpoint detection rules (e.g., Sigma rule ID 9b3c1d1e-... for vssadmin deletion) are recommended (MITRE ATT&CK D3FEND).

ⓘ 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.