[email protected]

[Content by Gemini 2.5]

[email protected] – Technical Breakdown & Recovery Guide

(Extension typically used: .cerber, .cerber2, .cerber3 … evolving to .cerber6 and later .foo)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Exact File Extension(s): The Cerber strain behind [email protected] historically appends .cerber## (where “##” is a two-digit version, e.g., .cerber, .cerber2, .cerber3). After version 6 it switched to a pseudo-random 4-character extension (.foo, .abcd, .beef, etc.) and used the same e-mail in the ransom notes.
  • Renaming Convention:
  1. File is encrypted with AES-256 (key wraps via RSA pub key).
  2. File structure becomes: <original name>.<ext>.cerber## (or later <name>.<ext>.beef, etc.).
  3. A new file named README.hta, README.html, !READ.htm, or # DECRYPT MY FILES #.txt/vbs/bmp/lnk is dropped in every directory; inside, the QQ e-mail address [email protected] (sometimes [email protected] alias) is shown under payment instructions.

2. Detection & Outbreak Timeline

  • March 2016 – Cerber v1 publicly disclosed, with.cerber extension.
  • Middle 2016 – Rising distribution via the affiliate “Ransomware-as-a-Service” model; e-mail [email protected] begins appearing.
  • September 2016 – Version 6 (.cerber6) released; voice ransom-note playback, QQ communications still used.
  • Early 2017 – Multiple 4-character extensions phase begins; China-centric contact e-mail persists.

3. Primary Attack Vectors

  • Phishing: Weaponized Office macros (invoice.exe, PaymentReceipt.doc) that download the DLL/EXE via PowerShell.
  • Exploit Kits: Rig, Magnitude, Radixu, and Neutrino EK dropping Cerber.
  • RDP / Remote Desktop Bruteforce: Attackers scan port 3389, break weak credentials → drop Cerber payload.
  • EternalBlue/SMBv1: Occasionally chained (public PoC scripts) after successful credential harvesting, primarily to move laterally.
  • Dropped by other malware: Manual installs after Emotet, Dridex, or Gootkit infections.

Remediation & Recovery Strategies

1. Prevention

  • Disable Office宏 unless digitally signed.
  • Enforce Network segmentation & restrict SMBv1 (set ScOnlyIPs or turn off SMB1 via Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
  • Use Lateral Movement Defense (least-privilege, restrict RDP to VPN, enable NLA & complex passwords).
  • Deploy modern anti-ransomware defense (CrowdStrike, Microsoft Defender ASR rules “Block process creation from Office”, etc.).
  • Segment admin credentials (Azure AD CA / Tiered privileged access).
  • Regular, off-site/immutable backups (3-2-1 rule) and test restores monthly.

2. Removal

  1. Immediately: pull network cable/disable Wi-Fi to stop further encryption.
  2. Boot into Safe Mode with Networking (or via Windows Recovery Environment).
  3. Identify the running process (often <digits>.exe in %appdata%\<guid>\ or %temp%).
  4. Use reputable anti-malware scanner (ESET System Rescue, Malwarebytes ADW/Ransomware Remediation, Kaspersky Rescue Disk).
  5. Delete the malicious folder & any scheduled tasks created in Task Scheduler\Microsoft\Windows\Setup\Scripts or Registry HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run.
  6. Run sfc /scannow and Windows Update to verify integrity before re-connecting to network.

3. File Decryption & Recovery

  • Is decryption free today? – Yes, but only for older versions (up to .cerber5/.cerber6) through publicly released master keys.
  • Tool: Trend Micro RakhniDecryptor 1.18+ (includes Cerber) – https://go.trendmicro.com/ransomware-decryptor/
  • Alternate: Avast Decryptor for Cerber – https://www.avast.com/ransomware-decryption-tools
  • Run on original machine or a newly-wiped Windows 10 VM from encrypted files/kept original versions.
  • Versions beyond 2017 (4-char extensions, e-mail [email protected]) remain encrypted offline without known keys.
  • Only avenues are: clean backups, Shadow Copies (via vssadmin list shadows or ShadowExplorer), or full volume snapshots (Veeam immutable repository / Windows Azure VM – Azure Backup).

4. Other Critical Information

  • Unique Characteristics:
  • Uses SQL-like audio ransom-note via text-to-speech (“All your files were encrypted”).
  • Deploys also a Tor-to-Web proxy (tor2web.org URLs) inside ransom notes for victim payment pages.
  • Deletes Shadow Copies via vssadmin delete shadows /all /quiet, disables Windows Defender in memory, and injects into 32-bit processes to bypass AV.
  • Wider Impact:
  • One of the first RAAS kits to hit enterprises plus consumers simultaneously; affiliate program allowed anyone to sign up, causing explosive global infections.
  • Notable attacks on US healthcare, Japanese manufacturing, Eastern European government servers.
  • Payment wallets show ~US $200-400 per decryption, but total losses reached tens of millions USD.

Quick Reaction Checklist (Pin to SOC/Help-desk)

  1. Isolate infected PCs immediately.
  2. Check Shadow Copies within shadow expiry time = 14 days default OB.
  3. Download the latest Trend/Avast offline decryptor and test on a test file before mass run.
  4. Clear IE cache / PowerShell execution policy back to Restricted to avoid reinfection via scripts hidden in browser history.
  5. Reset local admin passwords company-wide if brute-force vector suspected.
  6. Patch & harden host firewall – ensure SMB outbound 445 blocked to internet, RDP limited to jump hosts/VPN.

Stay vigilant—Cerber campaigns have largely ceased, but the toolkit and its contact e-mails resurface in copy-cat strains. The combination of decrypted master keys (old engine) plus solid backup hygiene will protect against this legacy threat.