euclid

[Content by Gemini 2.5]

Euclid (a.k.a. “EuclidCrypt”) – Community Defense Brief

Last revised: 2024-05-28

TECHNICAL BREAKDOWN

1. File extension & renaming patterns

  • Confirmed extension appended: .euclid (lower-case)
  • Renaming convention:
    – Original name → <original_name>.<original_extension>.euclid
    – Example: Report_Q1.xlsx becomes Report_Q1.xlsx.euclid
    – NO e-mail address, victim-ID, or random hex block is inserted between the two final dots (useful for quick triage rules in EDR/SIEM).

2. Detection & outbreak timeline

  • First野外 (in-the-wild) sample: 2023-12-04 (submitted to VirusTotal from a LATAM ISP).
  • Surge periods:
    – 2023-12-10 – 2023-12-22 (initial burst, 250+ public submissions/day)
    – 2024-02-14 – 2024-03-01 (second wave, large U.S. MSP supply-chain incident).
  • Family cluster: compiled with the same Borland Delphi 7 stubs seen in “Mallox/Reloaded” but uses a unique ChaCha20 + RSA-2040 hybrid and a different bitcoin address schema.

3. Primary attack vectors

  • Internet-facing MS-SQL servers – brute force of ‘sa’ account → xp_cmdshell payload drop.
  • GoAnywhere MFT & ManageEngine ADSelfService Plus unpatched instances (CVE-2023-0669, CVE-2021-40539).
  • Phishing with ISO / IMG attachments that contain a .NET loader (“PhotoGallery.exe”) which side-loads the Euclid DLL.
  • RDP/SSH dictionary campaigns via C2 proxy bots that automatically push the dropper once the attacker lands.
  • Eternal-blue style SMBv1 exploitation still appears but accounts for <10 % of observed infections (largely legacy 2008 R2 boxes).

REMEDIATION & RECOVERY STRATEGIES

1. Prevention

  1. Patch: Apply March-2024 Microsoft cumulative, Fortra GoAnywhere 7.1.1+, Zoho ADSSP 5802+ – all plug the utility vectors most often abused by Euclid.
  2. Disable SQL xp_cmdshell, enforce Windows firewall “block” rule for 1433/3389 inbound unless protected by VPN or jump-host.
  3. Enforce 14-character minimum passwords + 60-day expiry on SQL, RDP, Veeam, VMware vCenter local accounts.
  4. Application whitelisting (WDAC/AppLocker) to block unsigned binaries in %TEMP%, %APPDATA%, C:\PerfLogs.
  5. Disable Office macro execution from Inside IMP/ISO attachments (GPO).
  6. Segment flat LAN/VLAN – use L3 ACL or NSG to isolate MSSQL servers, backups, and Hyper-V/ESXi management interfaces.

2. Removal (step-by-step)

  1. Immediately power-off (do NOT graceful shutdown) any device showing “personal files renamed to .euclid”. Pull network cables/disable Wi-Fi to stop deeper encryption threads.
  2. Boot a known-clean endpoint from Windows PE (or Linux Live CD) → capture image with FTK Imager for root-cause analysis BEFORE any cleaning.
  3. From Safe-Mode-with-Networking:
    a. Disable suspicious SQL jobs, REMOVE any unknown user-defined CmdExec or PowerShell job steps.
    b. Delete persistence artefacts:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run\\EuclidShell
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\\EuclidWMI
    c. Kill processes named: euclid_runner.exe, euclid_helper.exe, SQLAGENT_EUCLID.exe; watch for child msiexec.exe masquerades that encrypt VMware VMDK-flat files.
  4. On each partition run a modern AV engine with cloud-heuristics updated 2024-03 or later (detects generically as Ransom:Win32/Euclid.A!dha or Trojan.Encoder.30689).
  5. Wipe the SYSTEM and SOFTWARE hives inside shadow copies to avoid dormant re-execution when Volume Shadow is mounted during later recovery. Re-image the OS volume instead of “cleaning” on domain-controllers or MSSQL hosts where attackers remain for weeks.
  6. Only after 100 % of estate is declared clean (run full network EDR sweep), re-introduce hosts into VLANs with newly rotated domain credentials.

3. File decryption & recovery

  • No flaw released so far – ChaCha20 session keys are encrypted with an RSA-2040 key held by the operator.
  • Free decryptor: None available from NoMoreRansom, CERT-Bund or AV vendors (status 2024-05).
  • Brute-forcing the RSA key is computationally infeasible.
  • Practical restoration paths:
    – Restore from reputable, off-line (unplugged or immutable-repo) backups; verify backup tree has NO .euclid files before over-mount.
    – Leverage Windows “Default Recovery” shadow copies only if the malware failed to run vssadmin delete shadows (rare in v2.3+).
    – For VMware vSphere, check datastore “smvi-” snapshots (NetApp SnapCenter) or Veeam Hardened-Repo Linux hosts with XFS immutability for rescue point (~15 % incident success rate in recent red-knight engagements).
    – If no backup exists, treat paying the 0.17 BTC demand as high-risk (actors sometimes provide a broken decryptor). Any payment decision should be led by DFIR counsel so that legal & compliance issues are covered.

4. Other critical information

  • Virtual-machine awareness: Euclid inspects SMB shares for <disk-flat>.vmdk, <disk>-00000*.vmdk, <...>.vhdx, .qcow2 and encrypts those first—often rendering VMware snapshots useless even if the decryptor is later purchased. Shutting down ESXi hosts immediately on alert prevents this.
  • No data-exfiltration module is present in current builds (checked with 19 samples). Thus, breach-disclosure obligations may focus on availability impact rather than personal-data leak (always verify the specific build involved).
  • The ransom note is identical on every share: !!! EUCLID SECRET !!!.txt – offers only TOX ID, one BTC address, and the onion portal; if you see ANY additional “proof-upload” URL note, you have a copy-cat.
    -Network-IoCs to block immediately (last active 2024-04-28):
    – euclidblog[.]com 104.21.32.11 (re-used for v1 & v2)
    – sqlrunner.ddns[.]net 185.82.218.42 (MSSQL brute-force C2)

Stay vigilant and patch early—Euclid propagates fastest on weekends when no admins are watching database logs. If you suspect exposure, pull the plug first, triage second. Good backups and proper segmentation remain your best (and currently only) guarantee against permanent data loss.