cerber3

[Content by Gemini 2.5]

Technical Breakdown – “Cerber3” (extension .cerber3)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by this strain acquire the .cerber3 suffix to the end of the original extension, e.g.,
    Report_2024Q3.xlsx.cerber3, vacation.jpg.cerber3.
  • Renaming Convention:
  1. Original file name and internal structure are preserved exactly—no base-64 renaming like later strains.
  2. Folder-level marker files # DECRYPT MY FILES #.html, # DECRYPT MY FILES #.txt, and # DECRYPT MY FILES #.url are dropped in every affected directory and the desktop.
  3. The wallpaper is silently changed to a yellow/red collage with the caption “CERBER 3 Ransomware”.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    • August 24, 2016 – CrowdStrike labs flagged the first dropper binary.
    • Throughout September – October 2016, affiliate campaigns massively pushed the variant via Rig-V exploit kit and phishing waves.
    • Tapered off by late Q4-2016 following public release of Kaspersky’s decryption utility and law-enforcement takedowns of some master C2 proxies.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Exploit Kits: Rig EK and Neutrino (Flash & Silverlight exploits CVE-2016-0189, CVE-2016-1019).
  2. Malicious Office macros (.docm) delivered in themed ZIP e-mails purporting to be receipts/invoices.
  3. RDP brute-force against weak or default passwords, then lateral movement via WMIC (wmic /node:...).
  4. EternalBlue (MS17-010) did NOT ship with Cerber3, but operators occasionally chained it in later lateral-movement phases.
  5. SMBv1 shares, removable USB (via autorun remnants on older Windows).

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
    • Patch Adobe Flash, Silverlight, Microsoft Office, Windows to August 2016-or-newer patch level.
    • Disable macro execution in Office by default.
    • Apply complex (pass-phrase) passwords to RDP and restrict 3389 behind VPN/Zero-Trust.
    • Segment networks with SMB access controls; disable SMBv1 across estate (Set-SmbServerConfiguration –EnableSMB1Protocol $false).
    • Deploy an application-control/whitelisting solution (e.g., Microsoft Applocker 3.x) blocking executables in %AppData%, %Temp%\*.exe.
    • Maintain an off-site, offline backup plus test failure drills monthly.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Unplug network cable / disable Wi-Fi to stop lateral spread.
  2. Boot into Safe Mode with Networking.
  3. Identify the persistent rundll32.exe / svchost.exe hosting cerber.exe or random-name *.dll launched via HKCU\...\Run\[randomUUID].
  4. Delete registry keys and scheduled tasks (schtasks /delete /tn "SystemRemInd*).
  5. Run Microsoft Defender offline scan or Kaspersky Rescue Disk to purge shadow copies re-infection vectors.
  6. Verify integrity: run sfc /scannow; may need re-image if system files are damaged.

3. File Decryption & Recovery

  • Recovery Feasibility: Completely feasible. Cerber3 used a vulnerable server-side key-generation scheme.
  • Tools:
    • RannohDecryptor 1.1+ (Kaspersky) – official, high-success utility released Nov 2016.
    • Decrypter for Cerber v2/v3 (avast! v2.3.0) – alternative with GUI; option to preserve encrypted originals.
    • Key Id extraction: Open any .html ransom note → inspect the <div id="public_key">XXXYYYZZZ</div> – paste into the decryptor when prompted.
  • Prerequisites:
    – Victims must retain at least one intact copy of an encrypted file plus its clear-text original (helps statistical validation).
    – Machine must be cleaned first to prevent re-encryption.
    – No need to pay – decryption keys are gre­nerated client-side then transmitted over HTTPS; Kaspersky’s exploit re-assembles them offline.

4. Other Critical Information

  • Unique Characteristics:
    • Uses text-to-speech through a Windows TTS engine to announce “Attention! Attention! Your documents, photos, databases and other important files have been encrypted…” on every boot.
    • Config file (C:\ProgramData\YYY\cfg.ini) contains ID + target-file extensions list (650+ file types), but file path is randomized for each run.
    • Cerber3 lacks the .hta dropper of Cerber 4/5, making it slightly easier to block via simple firewall rules (it uses hard-coded koi5bv.pw, okrew.pw, etc.).
  • Broader Impact / Notable Events:
    • Depression September 2016 of affiliate ID #91 alone reported 500+ victims across 16 countries.
    • Healthcare ransomware surge in U.S. mid-west clinics attributed to this strain via email phishing; HHS issued an alert (AC-2016-201).
    • The decryption release in November 2016 cut net earnings of the Cerber RaaS by an estimated 70 % and accelerated operator migration to Cerber 4, 5, and eventually Magnitude.

Quick One-Pager Poster for End-Users (publicly shareable):

  1. Your files have .cerber3 → DO NOT PAY.
  2. Disconnect, do not reboot.
  3. Download Kaspersky RannohDecryptor on a known-clean machine, transfer via USB.
  4. Run decryptor, browse to any encrypted location, supply ID from ransom note public_key=.
  5. If successful, move restored files to a new folder, format disk, reinstall Windows with full patches.
  6. Enable daily Veeam / Acronis / Windows Image Backup TO AN EXTERNAL AIR-GAPPED DRIVE.

End of advisory – please mirror widely and keep backups patched.