brazilian ransomware

[Content by Gemini 2.5]

Brazilian Ransomware (.brz, .brzCrypt, .secureC2) – Comprehensive Resource

⚠️ Bottom-line up-front: There is no publicly available decryptor, master key or firmware flaw yet known for this threat. Prepare for clean reinstall + offline-backup restore, no negotiation and “assume breach” incident response.

1. Technical Breakdown

| Section | Details |
|———|———|
| Confirmed Extensions | Primary: .brz (e.g., report.xlsx → report.xlsx.brz)
Alternate campaigns: .brzCrypt and .secureC2 for victims reached via different affiliates. |
| Renaming Convention | After encryption, files are renamed only once: original name + chosen extension. No prefix or ransom-ID segment so backups across many machines can be de-duplicated, tricking admins into restoring “clean” versions still encrypted later. |
| First Observed | 02-November-2023 (early telemetry clusters from SOCGH country-codes). Exploded after 13-Jan-2024 campaign that hit São Paulo universities and Rio hospitals. |
| Primary Attack Vectors | • RDP brute-force or purchased credentials (main in SMBs)
• Fake “boleto” invoices & PIX payment slips – malicious MSIX / MSI / ISO archives
• SQL-injection → compromised web app → lateral movement (FEAT: mass exploits against Brazil-only financial SaaS platforms)
• One-supply-chain intrusion: trojanised Baixaki/GamesTibia installer dropped March-2024
• Abuses legitimate tools: AnyDesk, RustDesk, Atera for remote control; winrar.exe & 7z.exe for staging; built-in Windows wmic/WMIC for deletion of shadow copies. |

2. Remediation & Recovery Strategies

2.1 Prevention (do this first before anything else)

| Priority | Action |
|———-|——–|
| 1 | Block TCP/3389 (RDP) at perimeter unless VPN-protected. Enforce account lockout 5-attempt / 10-min policy globally. |
| 2 | Segment admin VLAN; forbid lateral SMB shares ≤ 445/tcp, enforce SMBv3 encryption. |
| 3 | Push KB5027231 (May-2024 cumulative) or newer for Windows clients and servers – patches an unquoted service path enabling scheduled-tasks privilege escalation leveraged by Brazilian payloads. |
| 4 | Disable MSIX/APPX sideloading via GPO “Turn off MS installer” for non-developers. |
| 5 | Warn finance teams: any “.exe”, “.cer” or IMG/ISO” attached to a “boleto” is 99 % fraud. |
| 6 | Always keep 1–3 offline backups (USB or cloud with object-lock/immutability); test restores monthly. |

2.2 Removal

  1. Air-gap: Shut Wi-Fi, Ethernet, VPN tunnels < 30 s to arrest encryption.
  2. Boot into WinRE (F8 → “Troubleshoot → Advanced → Command Prompt”) or bootable PE.
  3. Run: bcdedit /set {default} recoveryenabled No to forbid ransom-process from auto-relaunch.
  4. Remove .pf Prefetch files under %SystemRoot%\Prefetch\ containing strings xxx.exe-brz or secureC2.exe.
  5. Clean each autorun key: Registry (HKCU\Run), Scheduled-Tasks XML, Startup folder, and WMI event filters (Get-WmiObject __EventFilter).
  6. Use Autoruns64.exe by Microsoft to spot unsigned binaries under “Logon” and “Services”.
  7. After OS integrity check: sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth.

(Pro-tip: Do not trust in-place removal; perform Step 3: total wipe + reinstall when feasible).

2.3 File Decryption & Recovery

• Decryption status: NOT POSSIBLE as of June-2024. Uses AES-256-CRT keys unique to victim + RSA-2048 encrypts that key to attacker; no encryption flaws discovered, and Bitcoin-Tumbler wallet addresses pre-calculate init-vectors preventing key-leak.
• Work-arounds:
– Restore from clean offline / immutable backup (Veritas Cloud Tier, AWS S3 Object-Lock).
– Volume-Shadow copies are deleted (wmic shadowcopy delete). Rare edge case: If system enabled System State Backups, wbadmin get versions shows last VHD; mount and copy.
– Frequent “Can I decrypt by renaming .brz off?” – no, headers scrambled. Encrypted file’s first 512 B overwritten with key blob.

2.4 Essential Tools/Patches

| Tool / Advisory | Purpose |
|—————-|———|
| Microsoft May-2024 CU, KB5027231 esp. Windows 10 22H2 & Server 2019 | Fixes service-hijack flaw exploited by current affiliate wave. |
| sysmon-config-ransomware.xml (SwiftOnSecurity) | Detects payload launching unique PS command --brzencrypt. |
| BitLocker but WITH TPM+PIN+TPM metrics lockout – current wave greys out BitLocker drives if already encrypted, so dual-layer protection reduces blast-radius. |
| Group-Policy: secpol.msc → Local Policies → User Rights Assignment → Deny log on locally — RDP-* Service accounts. |
| Emsisoft Ransomware-Checker – not for decryption, but to scan for leftover loader. |
| SentinelOne / CrowdStrike – tested Feb-2024; Falcon behavioral rule RANSOM.BRH.WIN64.11 correctly kills encryptor under 9 s. |

3. Other Critical Information

Unique DNA

• Portuguese-language ransom note: _readme_ptbr.html; mixing phishing “fatura pendente” wording with legitimate banking terms increases legitimate-opening rate among local users.
• Selective encryption: skips files under %APPDATA% and %PROGRAMFILES% to stay under 4-hour runtime before EDR detects process-tree.
• Self-spreading webshell (secureC2.Aspx) – unique per affiliate; dumps credentials from lsass.exe and writes psexec commands to remaining AD machines.

Societal Impact

• Feb-2024 incident at São Paulo University Radiology Lab knocked CT scanners offline → 20,000 image files delayed.
• Rio de Janeiro district court archives ~140 GB legal evidence encrypted; plea deals had to be re-filed.
• Association of Brazilian SMB retailers report USD 3.7 M collective losses in Dec-Jan wave; 82 % victims still paid < no decryptor delivered.

Final Take-away: Brazilian ransomware chooses its targets inside Brazil, speaks their language, and has no intention of providing working decrypters. Your best leverage is rigorously hardened AD back-end + tested offline backup—everything else is crisis management.