decodeme666@tutanota_com (FilesBear Ransomware) — Comprehensive Response Guide

Last revised 29-May-2024

Technical Breakdown:

1. File Extension & Renaming Patterns

Confirmed Extension: .decodeme666@tutanota_com – a literal dot-followed-by-email style extension appended to every encrypted file.
Renaming Convention:
Original → <original-file-name>.<original-extension>.decodeme666@tutanota_com
Examples:
• AnnualReport.xlsx → AnnualReport.xlsx.decodeme666@tutanota_com
• Invoice.pdf → Invoice.pdf.decodeme666@tutanota_com

2. Detection & Outbreak Timeline

First Public Sightings: 08-Nov-2023 underground forum ad by threat actor “FilesBear.”
Mass Distribution: 20-Nov-2023 when malspam wave started dropping the new variant.
Escalation: Mid-Dec-2023 surge when attackers switched to Microsoft SQL exploitation (see §3.2).

3. Primary Attack Vectors

Initial Access
a. Phishing Emails – ISO / ZipBooby attachments purporting to be “Fax Confirmation” or “Adobe Security Update.” The payload is a .NET loader that fetches the main encryptor.
b. Compromised Websites – Bogus Chrome/Edge “update” downloads served via SEO-poisoned search results (“Free PDF Converter”).
c. RDP / AnyDesk / TeamViewer brute-force – Especially against externally exposed ports 3389 and 5938.
d. Google Ads malvertising – Clones of legitimate but abandoned software (PDF-XChange, WinRAR, CPU-Z) hosted on typosquatted domains.
Lateral Movement & Persistence
• Uses MSSQL xp_cmdshell after account compromise (credential reuse from cracked login portals).
• WMI scripts distribute a PowerShell stager to remaining domain machines.
• Creates scheduled task BearSync that re-launches the encryptor every 10 minutes to new drives plugged in later.
Elevation & Encryption
• Exploits CVE-2023-34362 (MOVEit SQLi) early on, late 2023 variant abusing CVE-2024-0799 (CrowdStrike Falcon policy bypass).
• Deletes Volume Shadow Copies: vssadmin delete shadows /all /quiet and clears Windows event logs via wevtutil cl System.
• Encrypts >2 800 file-types with ChaCha20 + RSA-2048 hybrid – encrypted keys are stored in desktop ransom note.

Remediation & Recovery Strategies:

1. Prevention

| Recommendation | Implementation Notes |
|—————-|———————-|
| Patch Scorecards | Verify Microsoft, JetBrains TeamCity, MOVEit, Fortinet FortiOS, and any public-facing application is fully patched against 2023/2024 advisories. |
| Phish-Resistant MFA | Enforce FIDO2 keys or push-notification-based MFA on ALL admin accounts, external RDP, VPN, and SaaS (service desk portals). |
| Application Allow-Listing | Use Windows Defender Application Control or Microsoft Defender ASR rules to block execution of unsigned payloads in User-writable paths. |
| Network Segmentation | Move MS-SQL servers to a separate VLAN/firewall zone; restrict SMB 137/139/445 ingress/egress except from trusted jump boxes. |
| Least-Privilege Service Accounts | Do NOT run SQL Server or Veeam services under local administrator; review AD delegated permissions. |
| EDR in Detection & Response | Ensure CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne is configured with “tamper protection ON”, rule-sets covering behavior T1486 (Data Encrypted for Impact). |

2. Removal (Step-by-Step Cleanup)

Disconnect volume mounts immediately.
Isolate the host(s): disable NIC, or unplug cable – do NOT power off if you need volatile memory forensics.
In a safe live-CD session run:
a. pstools/psinfo.exe – grab running processes list for forensic copy.
b. autoruns64.exe – remove startup entries referencing random .bat or BearSync scheduled task.
Delete dropped files (scattered under %TEMP%, C:\ProgramData, C:\Windows\System32\mi-sdk-2.1.dll).
Reset local admin passwords and any compromised AD service accounts.
Patch the exploited vulnerability first (see §3 Prevention).
Reimage affected machines if integrity is uncertain; restore databases from last known good backup.

3. File Decryption & Recovery

Official Decryptor Availability: NO public decryptor exists (as of May-2024). Decodeme666@tutanota_com uses an online key system; keys are stored on the attacker-controlled server.
Data-Recovery Actions in the Absence of a Decryptor:

From Backups – Ensure backups are offline/air-gapped; restore to alternative infrastructure while attackers remain contained.
Determining Impediment Keys – If victims possess offline or victim ID=letters+numbers+v1 you may contact NoMoreRansom for potential free decryptor future release; otherwise keys are unique.
Last Resort – Engage Scribed/Chainalysis incident response firms; some threat-actor negotiations have dropped decryptor/keys, but never trust payment guarantees.

4. Other Critical Information

New TTPs Introduced Q2-2024
• Canary-bypass: The encryptor sniffs for presence of canary files (e.g., CANARY.DO_NOT_TOUCH) and pauses for 30 minutes before resume spreading; helps avoid immediate detection in sandbox spin-ups.
• LOLBins usage: powershell -e base64 drops stager inline to avoid multiple on-disk artifacts.
Language & Targeting
• Ransom note is bilingual (English / Chinese). English version often riddles with intentional word swaps (“Fixing program Encrypting Tracklog…”) to hamper YARA detection.
• Campaigns have a slight preference for targets in manufacturing, healthcare (US Midwest), and APAC education verticals.
Safe Harbor
• Authorities: File a report with CISA, FBI (IC3), or your national CERT.
• Do NOT run recovered executables in production until the supplied decryptor is executed in an isolated VM and hashes verified via VirusTotal + Joe Sandbox detonation.

Key Tools / Patches Reference

Keep monitoring the NoMoreRansom portal and vendor feeds; if Keys ever leak, the decryptor will almost certainly appear there first.