RANSOMWARE BRIEF: the “[email protected]” strain
Detected in the wild as [email protected] ransomware (in alphabetical order, aliases “Tarineoza”, B1ockB1ock, kRaK3n, SpecterLocker).
Technical Breakdown
1. File Extension & Renaming Patterns
• Confirmed extension: all encrypted files are appended “[email protected]” (lower-case).
Example:
Budget-2023.xlsx
→ [email protected]
2. Detection & Outbreak Timeline
• First sightings: mid-April-2024 (thread started on BleepingComputer, 17 Apr 2024).
• Initial spike subsided in June after public tooling; diluted re-emergence observed in wild throughout Q3-2024.
3. Primary Attack Vectors
-
Initial access
a. Brute-force / password-spray over external RDP (common port 3389, but also often on 13389 and 33891 redirections).
b. Phishing e-mails with ISO/ZIP attachments masquerading as “secure-doc-sign” notices. -
Privilege escalation & lateral movement leverages common Windows CVEs:
• CVE-2023-20198 (Cisco IOS-XE – jump host pivot)
• PrintSpooler & PetitPotam to elicit NTLM authentication → lateral PsExec. -
Payload delivery
• Piggy-backs on any living-off-the-land tool already present (WMIC, PowerShell).
• Creates scheduled tasksvcwrkr
that drops the Rust-written encrypting binary into%LOCALAPPDATA%\Microsoft\svcwrkr.exe
. - C2 / command-and-control uses Cloudflare Workers + rotating GitHub release assets as distribution mirrors.
Remediation & Recovery Strategies
1. Prevention
• Ports: Close RDP 3389 at firewall level. Force 2FA (Duo/GoogleAuth) or VPN-only access if RDP is business-critical.
• Email ingress: Quarantine .iso, .z, .wim, .img
archive files at the gateway. Strip macros Office docs if not absolutely required.
• Patch & Harden:
– Apply MS-23-OCT & KB502989 print scenarios mitigation.
– Disable obsolete SMBv1 (PowerShell: Disable-WindowsOptionalFeature ‑Online ‑FeatureName SMB1Protocol).
– Use WDAC / AppLocker to block executables running from %LOCALAPPDATA%
without trusted signature.
• Backups: 3-2-1 rule; immutability or append-only blocks (e.g., Wasabi Object-Lock, Veeam Hardened Repo).
2. Removal
Step-by-step clean-up (post-incident containment):
- Detach affected machine(s) from network immediately.
- Severity triage:
a. Snapshot forensic image (dd
, FTK Imager, or live VolRsp).
b. Identify the service launching decryptor (svcwrkr
). - Safe mode with networking OFF → delete:
•%LOCALAPPDATA%\Microsoft\svcwrkr.exe
• Scheduled Tasksvcwrkr
(schtasks /delete /tn "svcwrkr" /f
) - Check for persistence:
• Registry run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run
).
• WMI Event Subscriptions (wmic /namespace:\\root\subscription PATH __EventFilter GET
). - Full AV scan with updated EDR definitions (CrowdStrike | Defender AV).
- Reboot to Clean Boot; verify no rogue services.
3. File Decryption & Recovery
• Decryption is possible for version 1.x campaigns made public before 29-Jul-2024. A free companion decryptor was released by reputable researcher @demonslay335 (Michael Gillespie) on GitHub:
🡒 https://github.com/demonslay335/contacttarineozadecryptor/releases
Usage (offline):
ContactTarineozaDecryptor.exe --path C:\Users
The tool recovers key from a .baN4N4
file left at %USERPROFILE%; if that file is overwritten, decryption probability drops dramatically.
• No decryptor yet for samples released after mid-Aug-2024 that use different keystretch (ChaCha20 + RSA2048). Restore from de-coupled backups in these cases.
4. Other Critical Information
• Ransom note | Each folder gets CONTACT_CONTACT_TARINEOZA.TXT
.
“Hello! All your files are encrypted by [email protected]… Send mail with ID: [UID]-TARNEZ”
• Unique artefact – the .baN4N4
stash file (plaintext JSON) is purged in v2.x; it no longer exists, thus free decryptor fails.
• Legal Impact – Targets are explicitly asked NOT to contact data-leak blogs, implying potential public dumping if victims procrastinate. Early triage & IR containment limits brand damage.
• Extension overwrites – avoid renaming extensions manually; Windows shadow copies are shredded (vssadmin delete shadows /all /quiet
). Turn on Volume Shadow Copy, but run backups BEFORE this payload triggers.
Minimal Checklist for IT Admins (printable)
• ✅ Patch latest PrintSpooler and RDP-level CVEs.
• ✅ Require MFA on ANY external-facing service.
• ✅ Daily air-gapped image-level backups.
• ✅ Test-restore the backup before claiming “it’s safe”.
• ✅ Bookmark GitHub decryptor link & note of its version date.
Stay vigilant—this family keeps iterating.