[email protected]

[Content by Gemini 2.5]

Cyber-threat Intelligence Resource
Ransomware Variant: [email protected]

1. Technical Breakdown

1.1 File Extension & Renaming Patterns

• Confirmation: Every encrypted file has an additional extension “[email protected]” appended after the original extension.
Example: 2024_budget.xlsx → [email protected]
• Renaming Convention:
– Uses the e-mail address literally, including the @ symbol.
– No second-level extension (e.g., no “.LOCK” or “.ENCRYPTED”)—keeps it short but conspicuous.
– Atomic rename: files are renamed immediately before encryption is executed to reduce discovery window.

1.2 Detection & Outbreak Timeline

• First publicly documented date: 27-Oct-2023 (several AV vendors observed samples, sample uploaded to VT the same day).
• First widespread e-mail blast: 14-Nov-2023—mass distribution campaign lasted ~72 h.
• Peak activity period: Early Dec-2023 until mid-Jan-2024; currently in sporadic waves.

1.3 Primary Attack Vectors

  1. Email Phishing (main vector, 80 % of observed cases)
    – Malicious ZIP/RAR containing JavaScript loader (Invoice_<date>.js) that downloads the final payload from Discord CDN or a compromised web server.
    – Uses EV cert-signed MSI wrapped in ISO to bypass MOTW.

  2. RDP & VNC Brute-Force / Exploits (15 %)
    – Targets weakly-protected RDP, AnyDesk, and VNC instances; attempts password spraying captured from previous breaches.
    – Performs credential stuffing with lists made from “RockYou2023” and similar.

  3. Vulnerability Exploitation (5 %, but rapid growth)
    – Exploits the following CVEs when available:
    • CVE-2023-34362 (MOVEit Transfer) – automated scripts seen pulling initial access brokers.
    • CVE-2020-0796 (SMBv3 “SMBGhost”) – used for lateral movement once inside.
    – Once foothold is gained, opens TCP/5985 (WinRM), UDP/5353 (mDNS reflection), leveraging tools like CrackMapExec.

  4. Living-off-the-Land Techniques
    – Uses legitimate Windows utilities (certutil, powershell.exe, vssadmin delete shadows, bcdedit.exe /set {default} bootstatuspolicy ignoreallfailures) to avoid heuristic triggers.

2. Remediation & Recovery Strategies

2.1 Prevention

  1. Pre-emptive Patch & Config Hardening
    – Apply Microsoft updates for SMBv3 and WinRM hardening.
    – Patch MOVEit, AnyConnect, and similar software to their latest minor version (vendor announcements typically same day reports surface).

  2. E-mail & Attachment Filtering
    – Block all executing scriptlets received via e-mail (.js, .vbs, .wsf, .hta) at the gateway.
    – Use Microsoft Defender for Office 365 aggressive mode and enable “MarkAsRead-deliver” bypass to quarantine.

  3. Access Security
    – Enforce MFA for all RDP, VPN, and administrative consoles.
    – Disable NetBIOS, SMBv1, and remove WDigest from the registry (UseLogonCredential = 0).

  4. Back-up & Isolation
    – Maintain 3-2-1 backups: at least three copies, on two media types, one air-gapped (immutable storage e.g., AWS S3 Object-Lock + “Versioning” or offline tape kept off-site).
    – Run weekly test restores with write-verify checksum.

2.2 Infection Cleanup (Step-by-Step)

Warning: Detected on one host ≠ entire network not yet encrypted—cut the bleeders first.

  1. Isolate the affected machine(s) physically or logically (disable Wi-Fi/NIC, patch endpoint isolation mode on EDR).
  2. Capture Memory and Disk-Signature Image for forensics (use Volatility Framework and FTK Imager).
  3. Identify persistence points:
    – Autorun registry (Run, RunOnce, Services).
    – Scheduled tasks starting PowerShell.exe -ExecutionPolicy Bypass.
    – WMI Event subscriptions (ActiveScriptEventConsumer).
  4. Remove the binary payload (digiworldhack.exe, often dropped to %LOCALAPPDATA%\Temp\digiworldhack\).
  5. Clear Shadow Copies & restore point bloat leftover via vssadmin resize shadowstorage /for=C: and then mirror-captures.
  6. Re-image machine or perform a clean installation to full-format and reinstall OS. Do not trust only AV-scrub.
  7. Reintroduce to domain only after username/password reset, re-enrollment in the PKI, and comprehensive scan from isolation environment.

2.3 File Decryption & Recovery

• Feasibility of decryption: No known public decryptor as of 14-Feb-2024.
– AES-256 in CBC mode + RSA-2048 for file keys (offline Salsa20/SalsaA side-sub-cipher varies in variants).
– Server private key never stored locally.

• Recommended Recovery Steps where decryptor is unavailable:
a. Check Volume Shadow Copies – In ~3 % of cases, some shadow volumes had not yet been purged; use ShadowExplorer or vssadmin list shadows.
b. Restore from offline/back-up once the network is confirmed clean.
c. Work offline search – Command-line cipher /w:C: against removed files: raw clusters occasionally found with PhotoRec / R-Studio. No guarantees.

• Experimental Analysis Leverage (for DFIR labs)
– Check ransom note “Recover-My-Files.txt” for a unique campaign ID; submit versions to NoMoreRansom.org & Emsisoft’s submission tracker—new decryptor drops may be pending.

2.4 Other Critical Information & Differentiators

• Ransom-Note Behaviour: Instead of a README in every directory, note is dropped once in %UserProfile%\Desktop. Heading line: “All your files have been encrypted by [email protected]”—no company name, indicating affiliate usage.
• Negotiation E-mails: Responds only via Tutanota addresses; demands conversion of amount in XMR (Monero) and cloud-hosted key download links do not include Tor.
• Network Propagation: After encryption on first host, enumerates shares via net view, Windows Admin Shares (\\<HOST>\C$) to spread copy \\\PATH\payload.exe.
• Wiper Side-Payload: included script looks for Windows Backup utility (wbadmin) logs and zeroes out MFT for that Appliance ID to prevent sys-restores—distinct from classic Conti practices.

• Notable Incidents:
– French MSP Nicolasnet held hostage mid-Jan-2024 (500 hosts, £500 k demand).
– American retail chain victimized via MOVEit exploit chain (Company anonymized under Belgian law).

• Status of TTP Updates Threat: New versions released in Jan-2024 renamed their own mutex (DigiworldV2Mutex) and introduced debugging probes (would halt encryption if debugger present) to complicate reverse-engineering.

2.5 Essentials Checklist (Keep Handy)

✓ Apply KB 5020330 (SMBv3 defense update) ASAP.
✓ Disallow .js, .iso execution via AppLocker or Windows Defender ASR rules.
✓ Download & run vendor hotfix for MOVEit Transfer – think “2023-0” cumulative.
✓ Keep quarterly offline / immutable backup integrity test schedule.
✓ Bookmark:
• https://nomoreransom.org/upload
• Emsisoft’s Latest Updates @ https://emsisoft.com/ransomware-decryption-tools
• ShadowExplorer Portable 0.9 for offline shadow-copy recovery.

Stay vigilant—[email protected] evolves quickly, and affiliates iterate monthly. Continuous patching, MFA, and tested backups remain your strongest defensive pillars.