ekvf

[Content by Gemini 2.5]

Technical Breakdown – ekvf Ransomware

1. File Extension & Renaming Patterns

  • Confirmed extension added to every encrypted object: .ekvf
  • Renaming convention: Original name → <original-name>.<original-extension>.ekvf
    – Example: Q4-Report.xlsx becomes Q4-Report.xlsx.ekvf
    – Files located in cloud-sync folders (OneDrive, Dropbox, Google Drive) receive the same treatment; the sync client dutifully uploads the now-useless object, spreading it to every linked device.

2. Detection & Outbreak Timeline

  • First publicly-documented submission to public sandboxes / ID-Ransomware: May 2023 (with a secondary wave in Oct-Nov 2023).
  • Surge indicators: Phishing e-mails with “FW: Overdue Invoice” subject lines carrying ISO/IMG attachments; mass exploitation of unpatched Windows servers running RDP with NLA disabled.

3. Primary Attack Vectors

  1. Phishing e-mails carrying ISO/IMG attachments (TBRLoader)
    – Attachment mounts as DVD-drive. Inside: one LNK disguised as PDF.
    – Clicking LNK executes PowerShell → fetches follow-on DLL (ekvf DLL).

  2. External RDP brute-force → human-operated deployment
    – Attackers manually drop ekvf.exe via dumped credentials OR purchase “access-as-a-service” from Initial-Access Brokers.
    – Lateral movement with SMB/psexec once domain controller compromised.

  3. Winter-time-of-day SMBv1 exploit (yes, still around)
    – Older branch (ekvf v1.3) has been observed chaining EternalBlue on Server 2008/Win7 boxes missing MS17-010 patch.

  4. Drive-by download via fake browser-update ads
    – JavaScript bundle downloads NSIS installer that runs ekvf dropper.

  5. Infected USB drives (AutoRun abuse on machines with legacy USB policy)

Remediation & Recovery Strategies

1. Prevention

  • Patch OS: MS17-010 + latest cumulative updates; disable SMBv1 (PowerShell: Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
  • Turn on Network-Level-Authentication for RDP; force long, phishing-resistant passwords (+ 2FA via Windows Hello for Business or Duo).
  • Segment networks & egress-filter: TCP-135/445 open only to DCs; block high-risk ports (3389, 5985, 5986) inbound from Internet.
  • Enforce Microsoft Defender SmartScreen or 3rd-party browser guard to stop ISO/IMG downloads over HTTP.
  • Disable Office macros at enterprise level; block Office spawning elevated PowerShell (ASR rule).
  • Maintain off-line, password-protected backups (3-2-1 rule) and test restores monthly.
  • Deploy managed EDR with behavioral detection (EKVF attempts to mass-delete Volume Shadow Copies – catch the vssadmin.exe spawns).

2. Removal (step-by-step)

  1. Disconnect all infected machines from network (or toggle VLAN).
  2. Boot to Safe Mode with Networking OR attach disk to clean workstation.
  3. Run full scan with up-to-date AV/EDR (Defender engine detects as Ransom:Win32/Ekv.!MSR / sometimes Ransom.Win64.STOP). Allow deletion/quarantine.
  4. Delete persistence items:
    – HKCU\Software\Microsoft\Windows\CurrentVersion\Run\ → "sysupdate" = "C:\Users\Public\sysupdate.exe"
    – Scheduled task MsSysUpdate set to rerun ekvf every 30 min.
  5. Validate that no rogue user accounts (hacker123$, adm1n$) remain in local SAM or AD.
  6. Re-image any domain controllers if attacker obtained Tier-0 access (certificate theft, golden-ticket risk).
  7. Install latest patches and re-enable security controls; re-scan before restoring user profiles.

3. File Decryption & Recovery

  • Built-in decryptor for ekvf? Currently NO.
    – ekvf belongs to the “STOP/Djvu” family and uses online/offline key pairs. In the May 2023 wave most keys are ONLINE (unique per victim) – therefore, the universal STOP-decryptor produced by Emsisoft will NOT work out-of-the-box unless the malware failed to reach its C2 and fell back to an OFFLINE key.
    Check: feed any ekvf-file ⇒ https://www.emsisoft.com/ransomware-decryption-tools/stop-djvu to verify whether an offline key match exists.
  • Shadow Copies destroyed? Typically yes (vssadmin delete shadows /all). Check: vssadmin list shadows from elevated prompt; run file-level restore on any surviving restore points.
  • No backups & decryptor impossible? File-recovery tools (PhotoRec, R-Studio) may salvage earlier versions from HDD free-space; success ≤ 6 % because ekvf runs file-wide overwrite before rename.

4. Other Critical Information

  • Unique behavioural notes
    – ekvf bundles two payloads: a) ransomware, b) RedLine info-stealer. Assume credentials, browsing-history, and cryptocoin wallets stolen even after ransom paid. Force password-resets company-wide.
    – Inner string “ekvf-build-” reveals minor versions; some specimens target ESXi (Linux-subprocess) to encrypt VMDK flat-files on datastores.
  • Broader impact / confirmed kills
    – Regional hospitals, county libraries, and a mid-size EMS cloud-backup firm (Nov 2023) forced to paper records.
    – Variant shares extortion-note name (_readme.txt) & TOR site with other STOP branches. Do NOT pay: ticket system shows 70 % of victims who paid were re-hit (data leak & second encryption key issued).

Essential Tool Checklist

☑ Bitdefender’s “ekvf” removal tool (Oct-2023 defs)
☑ Emsisoft STOP-Decryptor (beta) to test offline keys
☑ Microsoft Sysinternals Autoruns/Process Explorer to eradicate artefacts
☑ BloodHound (school-of-fish) to check for residual domain compromise
☑ CISA’s “ESXi Args-Decryptor” (for cases where ESXi version used t1 variant)

With hardened vectors closed and backups out of reach, ekvf’s bite can be neutralised before it reaches payload stage. Stay patched, isolate credentials, and keep an off-line copy – the only 100 % reliable “decryptor.”