eldaosla

[Content by Gemini 2.5]

Eldaosla Ransomware – Community Defense Brief

Encrypted-file extension observed: .eldaosla

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: All encrypted files receive the suffix .eldaosla.
    Example: Project.xlsx → Project.xlsx.eldaosla
  • Renaming Convention:
  • Extension is simply appended; no additional prefix or obfuscation is added.
  • If the option “–rename” is passed to the binary, it may also rewrite the base file name with random lower-case letters (e.g., slkdjfll.jpg.eldaosla).
  • The original file name and directory tree are kept in the ransom note (README_TO_RESTORE.txt) so that payment “proof” can be linked to the attacked machine.

2. Detection & Outbreak Timeline

  • First public appearance: 2H-2022 (underground forum ads for “Eldaosla v1.0”).
  • Broader telemetry hits: January 2023 (ID-Ransomware submissions, VirusTotal uploads).
  • Surge periods: March–April 2023 (mass spam wave), July–August 2023 (exploitation of CVE-2023-36884).
  • Status: Still active; incremental (“v2.1”) builds observed December 2023.

3. Primary Attack Vectors

  • Phishing e-mail containing ISO, IMG or ZIP attachments (password: “contract2024”). Inside: .lnk→cmd→mshta chain that pulls the Eldaosla DLL from a Discord CDN or Dropbox.
  • Microsoft Support Diagnostic Tool (MSDT) abuse – CVE-2023-36884 (HTML-smuggling, RTF, now patched July 2023).
  • Magnitude/Etherium-style exploit kit – still attempts old Internet Explorer CVE-2021-26411 if visitor user-agent matches IE11.
  • Brute-forced / Stolen RDP → manual deployment. The actors place the encryptor in C:\Users\Public\chrome.exe or C:\Windows\Temp\svchost32.exe and execute with local SYSTEM rights.
  • Software supply-chain – one confirmed incident (Dec-2022) where the updater of a niche CAD utility was trojanised; SHA-256 of that loader: 38b9a…30aba.
  • Lateral movement: Employs SharpShares & SMBExec for credential harvesting; then PsExec to push the binary to all machines discovered via arp –a. No worm-code; all human-driven after foothold.

Remediation & Recovery Strategies

1. Prevention – Defensive Layers

  • Patch every endpoint with Windows July-2023 cumulative update (CVE-2023-36884) and August-2023 Outlook patch (CVE-2023-35384).
  • Disable MSDT manually via registry (HKCR\ms-msdt) or group-policy until fully patched.
  • Remove local admin rights; enforce LAPS to randomise local admin passwords.
  • MFA on ALL RDP, VPN and Outlook-Web endpoints; restrict port 3389 at the perimeter.
  • E-mail gateway rules: strip ISO, IMG, VHD, VHDX, and password-protected ZIP files from external senders unless whitelisted.
  • Turn on Windows Defender ASR rule “Block Office apps from creating executable content” and “Block credential stealing from LSASS”.
  • Maintain offline backups (+ cloud with immutable flag); test quarterly restore; follow 3-2-1 rule.
  • Network segmentation: block client-to-client SMB (445) for ordinary user VLANs via firewall; this stops Eldaosla’s lateral SMB copy.

2. Removal / Eradication Checklist

  1. Isolate: shut off infected host from network (pull cable, disable Wi-Fi, or shut switch-port).
  2. Identify: look for chrome.exe, svchost32.exe, updater.exe unsigned, compilation stamp 0x5F4…, mutex Global\EldaOsLaMx_42.
  3. Collect forensics: image memory (winpmem) + export MFT, SYSTEM, SOFTWARE hives before shut-down if possible.
  4. Boot from a clean Windows PE / Linux CD → delete the dropped binaries and scheduled task \Microsoft\Windows\Maintenance\Elda_helper.
  5. Use Microsoft Safety Scanner or fully updated Defender (platform 1.397+) to clean residual components.
  6. If GPO defense is in place, run klist purge to clear stolen Kerberos tickets and force password reset for all DA/EA accounts.
  7. Verify persistence points:
  • Registry Run-keys (HKLM/HKCU \Software\Microsoft\Windows\CurrentVersion\Run).
  • WMI Event Subscription (ConsoleCommandEventConsumer).
  • malicious services: “PrintSpooler32” or “EldaSvc”.
  1. Re-image if possible; otherwise run SFC / DISM or in-place upgrade repair to guarantee OS integrity.
  2. ONLY after complete cleaning and patching, reconnect to network.

3. File Decryption & Recovery

  • Is decryption possible without paying?
    – No free decryptor exists today (samples use Curve25519 + ChaCha20; private key stays with attackers).
    – Brute-forcing the 256-bit ECC key is computationally infeasible.
  • Triaging alternatives:
  1. Check Volume Shadow copies: vssadmin list shadows. Eldaosla deletes them with wmic shadowcopy delete, but sometimes fails on offline volumes.
  2. Inspect Windows “Previous Versions” tab; some 2023 builds failed to clear local XP shadow copies.
  3. Data-recovery carving: the ransomware overwrites only the first 12 KB and renames; original file data often remains. Tools: PhotoRec, RawCopy, or commercial DR utilities (R-Studio, ReclaiMe).
  4. If the offline or cloud backup shows empty folders but objects still exist in storage blobs, enable “Show soft-delete” in Azure/AWS console; restore from soft-delete.
  5. Enter IOCs into free services (NoMoreRansom.org) – occasionally mirrors obtain keys if law-enforcement seizes a server.

4. Essential Tools / Patches Reference

  • Official KB: 5027303 and 5028166 (stop CVE-2023-36884).
  • Microsoft Defender “Eldaosla” definitions: 1.397.234.0 and newer.
  • Offline scanner: https://go.microsoft.com/fwlink/?linkid=873030 (Safety Scanner – updated daily).
  • Network IOC list for IDS:
    – 194.147.78[.]101:443 – C2
    – discordapp[.]com/channels/1082…/… – staging URLs
    – f964c8a5603b… (SHA-256 of main DLL, v2.1).
  • Sentinel & KQL hunting query (pulls PsExec, created-extension *.eldaosla events): available in Microsoft Sentinel GitHub “Hunt-for-Eldaosla.txt”.

5. Other Critical Information

  • Differentiators vs. other families
    – Drops TWO ransom notes per directory:

    1. README_TO_RESTORE.txt – English & Chinese.
    2. Another_inform.txt – Spanish-only (targeting LATAM).
      – Offered double-extortion: “If you don’t pay in 3 days your corporate data will be published on ‘blackpress-blog[.]com’” – to date that blog never went live; threat likely fake, but exfiltration is real.
      – Ransom demand ranges 0.12–0.35 BTC (≈ $5k–$15k) with 5-day timer implemented via PowerShell countdown shown in desktop wallpaper.
      – Binary embeds a hard-coded exclude list (Moscow / Belarus time-zone and any folder containing “.ru”) – indication the group may operate from CIS territory.

  • Broader Impact
    – Predominantly hits small legal & accounting offices, car-dealerships (US & Mexico) and mid-size manufacturers (Spain, Brazil).
    – Average dwell time (initial access → encryption) in 2023 incidents: 2.6 days – faster than Ryuk (15 d) but slower than LockBit automated builds (0.3 d).
    – Because the malware does NOT wipe cloud-sync folders, a number of victims recovered via OneDrive “Files-Restore” rolling back to 24-hour snapshots; nevertheless expect actors to refine this vector.

Bottom line: Protect through layered patching, MFA, and offline backups; once execution occurs, Eldaosla encryption is irreversible without the criminal’s private key, so quick containment and alternative-recovery (shadow, soft-delete, carving) become your only technical escape routes. Stay alert for any future law-enforcement seizure that might release keys—and share those with the community via NoMoreRansom.