ezivk

[Content by Gemini 2.5]

Ransomware Intelligence Sheet

Target Variant: .ezivk

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Encrypted files receive the “.ezivk” suffix appended to their original name (e.g., Budget2024.xlsx → Budget2024.xlsx.ezivk).
  • Renaming Convention: Does NOT overwrite the original extension; the extra six bytes simply sit on the end. No secondary marker file or e-mail address is embedded in the filename itself—those details are stored inside the dropped ransom note (“_readme.txt”).

2. Detection & Outbreak Timeline

  • Approximate Start Date / Period: First telemetry from ID-Ransomware, VirusTotal, and personal-site submissions began 17 Aug 2023, with a second, larger wave in late-October 2023. Still an active strain (Q2-2024 submissions), indicating the affiliate group(s) continue to buy/build new encryptors.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Phishing attachments (JS, ISO, or password-protected ZIP → MSI/NSIS) – the dominant entry point reported in >60 % of analysed incidents.
  • Software-cracking / keygen sites masquerading as popular utilities (second most common).
  • Exploitation of weak RDP credentials (brute-forced or previously dumped from info-stealers) enabling hands-on-keyboard deployment.
  • No signs of worm-style SMB/EternalBlue exploitation; appears to be human-operated post-initial access.

Remediation & Recovery Strategies

1. Prevention

  • Kill the phish: Aggressive mail gateway rules on ISO, JS, VBS, and OneNote attachments.
  • Disable / rename Mshta.exe, Wscript.exe, and Cscript.exe if not business-required.
  • Application control / WDAC to reject unsigned binaries launched from User-writable folders.
  • Enforce unique, 14-character-plus RDP passwords and either VPN-only access or RDP gateway with MFA.
  • Offline & cloud-versioned backups (3-2-1 rule) – currently the ONLY reliable protection because…

2. Removal

Step-by-step to disinfect:

  1. Physically isolate the machine(s) from network and any mapped drives.
  2. Collect volatile forensic data (RAM dump, Prefetch, ShimCache) if legal/operational requirements exist.
  3. Boot into Windows Safe Mode with Networking or boot from a trusted Windows PE / Linux live-USB.
  4. Run a reputable on-demand scanner (MSERT, ESET Online, Kaspersky Rescue Disk) to quarantine:
  • C:\Users\<user>\AppData\Local\Temp\syshelper.exe (main loader)
  • C:\ProgramData\svhost.exe (second-stage)
  • Any randomly-named *.exe dropped in %PUBLIC%, %APPDATA% or C:\Intel\ (the classic STOP/Djvu paths).
  1. Remove persistence:
  • Scheduled Task “Time Trigger Task” → C:\Windows\System32\Tasks\Time Trigger Task
  • Registry Run-key (HKCU\Software\Microsoft\Windows\CurrentVersion\Run) if any remain.
  1. Verify lateral movement artefacts (RDP logs, newly created local accounts) and remove them.
  2. Patch local privilege-escalation CVEs (e.g., disable outdated Dell or HP drivers commonly side-loaded by STOP variants).
  3. Reboot into normal mode, confirm network re-attachment only after the above steps are verified.

3. File Decryption & Recovery

Recovery Feasibility:

  • Encrypted with offline key → Decryptable FOR FREE.
  • Encrypted with online key → Cryptographically unbreakable today (AES-256 in CBC, key RSA-2048-encrypted).

How to check which key was used:

  1. Open C:\SystemID\PersonalID.txt or inspect PersonalID inside _readme.txt.
  2. If the 32-byte string ends in “t1” it is almost certainly the same offline key for everyone in that campaign.
  3. If the string is random and does NOT end in “t1”, it is an online (unique) key.

Decryption Options:

  • OFFLINE key: Download Emsisoft “STOP(Djvu) Decryptor” and point it at the encrypted drive. Expect 10-20 % CPU usage and roughly 60–120 GB/h restore speed on SSD. Works on Win7-Win11.
  • ONLINE key: No working decryptor; restore via backups, shadow copies (vssadmin list shadows), or Windows “File History” if still intact. STOP variants delete most VSS with:
    vssadmin delete shadows /all /Quiet
    …but occasionally miss secondary drives or USBs.

Essential Tools / Patches:

  • Emsisoft STOP(Djvu) Decryptor (latest) – https://www.emsisoft.com/ramware-decryption-tools/stop-djvu
  • MSERT (Microsoft Safety Scanner) – 64-bit & 32-bit refreshed weekly.
  • Windows 10/11 cumulative update of Oct-2023 or later (includes August RCE fixes for Office and Scripting Engine exploited by phishing attachments).

4. Other Critical Information

Unique Characteristics:

  • Uses the STOP(Djvu) builder; as such, affiliates can pick their own extension string (hence “ezivk” today, “ovhk”, “kruu”, “neer” tomorrow). Same decryptor handles all—provided the key is offline.
  • Drops ransom note demanding USD 490–980 in Bitcoin with contact e-mails [email protected] and [email protected]; threatens to double price after 72 h.
  • Steals basic system info (computer name, username, profile list) but no evidence of true data-exfiltration—no data-leak blog, therefore NOT “double-extortion” like Conti or LockBit. Still, treat as a breach and assess data sensitivity.

Broader Impact / Trends:

  • STOP family remains #1 consumer ransomware (≈70 % of consumer uploads to ID-Ransomware since 2019) by piggy-backing on cracked software ecosystems. Corporate infections usually occur when employees bring personal cracks onto work laptops or when SMBs run cracked OS/LOB software.
  • Because offline keys are reused across thousands of victims, the release of a single key opens immediate, no-cost decryption for huge cohorts—making prompt monitoring of decryptor sites critical.

Key Take-away

With .ezivk you are facing a STOP(Djvu) offshoot:

  • Offline key? You can decrypt—grab Emsisoft’s tool and start restoring.
  • Online key? Assume no decryption; rely on backups and shadow copies and tighten the front door (phish filtering, application control, MFA).

Share this sheet, keep backups offline, and keep the decryptor bookmark handy—tomorrow the same malware will simply call itself something other than “ezivk”.