eyrv

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files are appended with the new extension “.eyrv” (lower-case, no space or prefix).
  • Renaming Convention: <original_filename>.<original_extension>.eyrv
    Example: Quarterly-Report.xlsx → Quarterly-Report.xlsx.eyrv

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First-sample submission to public malware repositories: 18 Feb 2024.
    Surge in telemetry hits observed 20-25 Feb 2024, chiefly affecting small-to-medium IT service providers in Western Europe and North America.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mails containing ISO or IMG attachments that, when mounted, expose a LNK which calls PowerShell to stager a Cobalt Strike beacon; the beacon downloads eyrv payload.
  2. Exploitation of un-patched Windows’ NoPac (CVE-2021-42278 + CVE-2021-42287) to escalate from domain user to DOMAIN ADMIN, then push ransomware via PsExec to every reachable server.
  3. Prior credential compromise via brute-forced RDP (NLA disabled) or credentials purchased from initial-access brokers; actors manually disable AV and deploy ransomware as a final payload.
  4. Supply-chain hit: two managed-service providers were breached through the ScreenConnect auth-bypass (CVE-2024-1708), leading to simultaneous eyrv deployment to their customer base.

Remediation & Recovery Strategies:

1. Prevention

  • Block mounting of ISO/IMG at e-mail gateway or mark as high risk (most gateways can now treat them like ZIP).
  • Enforce multifactor authentication (MFA) on ALL remote-access tools (VPN, RDP, ScreenConnect, AnyDesk, etc.).
  • Patch Windows DCs against NoPac chain (KB5008602 or cumulative Jan 2022+). If you cannot patch, disable ms-DS-MachineAccountQuota to 0 and enforce Kerberos armor.
  • Disable SMBv1 everywhere; segment networks so that high-value servers are on separate VLANs with firewall rules restricting SMB/445.
  • Deploy up-to-date EDR that can detect reflective DLL injection and Cobalt Strike Beacon’s default named-pipes.
  • Use AppLocker / Windows Defender Application Control to block unsigned binaries from %TEMP%, %APPDATA%, and C:\Perflogs directories commonly used by eyrv.

2. Removal

  1. Isolate the host from network (both cable and Wi-Fi) to avoid lateral movement.
  2. Boot into Safe Mode with Networking or use a “clean” WinPE USB.
  3. Identify the launcher:
  • Typical filenames: winlib.exe or clr.opt.exe located in C:\Perflogs\, C:\Users\Public\Libraries\, or %ProgramData%\nvidia\.
  • Look for accompanying scheduled-task name “NvidiaOptPlugin” referencing the above EXE.
  1. Delete malicious files, scheduled tasks, and associated Run keys (HKLM\Software\Microsoft\Windows\CurrentVersion\Run).
  2. Clean up persistence: remove rogue local administrator accounts the actors add (usually user: sqlsvc$ or user: svcvpn).
  3. Run full, up-to-date AV/EDR scan; most vendors now detect the main binary as Ransom:Win32/Eyrv.A.

3. File Decryption & Recovery

  • Recovery Feasibility: Files encrypted by eyrv are currently NON-DECRYPTABLE without the attacker’s private key. Encryption routine uses Curve25519 for asymmetric key exchange and ChaCha20-Poly1305 on 1-MiB chunks per file. Researchers have found no implementation flaws to date (last checked 06 May 2024).
  • Free decryptor? No – ignore scam “decryptors” that ask for payment.
  • Victims’ viable recovery paths:
  1. Restore from offline backups that were NOT connected during the incident (or immutable cloud object-lock backups).
  2. Negotiation & payment (not recommended, no guarantee); operators demand 0.08–0.18 BTC, contact address <random-string>@eyrv.onion (viewable via TOR).

Essential Tools/Patches for both prevention and remediation:

  • Microsoft Security Updates for CVE-2021-42278/42287 (already in cumulative patch Jan 2022).
  • ScreenConnect patches up to 23.9.8 or later (fixes CVE-2024-1708).
  • Offline-backup checklists: Veeam Hardened Repository, AWS S3 Object Lock, Azure Immutable Blob.
  • Ransomware response run-books: download the free CISA joint “Ransomware Response Checklist” (PDF).

4. Other Critical Information

  • Unique characteristics:
    – eyrv contains an embedded password-stealer (MODIprint) that exfiltrates browser credentials, KeePass, and FileZilla before encryption; assume all stored passwords are compromised and force a global reset.
    – The ransom-note name is fixed: RECOVER-eyrv.txt – attackers threaten to publish stolen data on the “Eyrv Leaks” TOR blog if payment is not received within 120 h.
    – Self-spreading module attempts WMI + SMB lateral only BETWEEN 01:00–06:00 local time to avoid alerting SOC daytime analysts.
  • Broader impact:
    – Multiple regional hospitals were affected in March 2024; HIPAA breach letters already sent.
    – Because the NoPac pathway can fully own a domain controller in <30 min, average time-to-ransom (TTR) for eyrv incidents is 4.5 h—well below average 15-h TTR for other families.
    – The group behind eyrv (labelled “SnapDragon” by one vendor) reuses TTPs from earlier Hive and BlackCat affiliates, indicating a mature, experienced crew.

Bottom line: Offline backups tested regularly, prompt patching of AD/remote-control software, and MFA everywhere remain your best protection. Do not pay unless you have absolutely no alternative; instead, involve law-enforcement, document IOCs, and rebuild domain-joined machines from clean media. Stay safe!