banta

[Content by Gemini 2.5]

Technical Breakdown

  1. File Extension & Renaming Patterns
    • Confirmation of File Extension: every encrypted file receives the suffix “.banta” (lower-case, no preceding dot-space).
    • Renaming Convention: the malware prepends an 8-byte hexadecimal victim-ID enclosed in square brackets to the original file-name, then appends “.banta”.
    Example:
    Original: Q3Financial.xlsx
    After: [A4F7B2C1]Q3    Financial.xlsx.banta

  2. Detection & Outbreak Timeline
    • Earliest reliable samples uploaded to VirusTotal: 19 July 2023.
    • First confirmed enterprise outbreak (pharmaceutical sector in LATAM): 21 Aug 2023.
    • Sharp uptick following exploit kit “Rig-EK” update observable 2 Sep 2023 → mid-September.

  3. Primary Attack Vectors
    • SMBv1/EternalBlue (MS17-010) – wormable intranet spread after initial foothold.
    • Phishing Campaigns – two large waves using ISO and IMG-mounted LNK lures.
    • Exposed & weak-credential RDPs (TCP/3389) – automatic brute-force lists (top-500 passwords).
    • Recent Confluence OGNL injection (CVE-2023-22515) observed as entry point in cloud-to-on-prem lateral movement scenarios.

Remediation & Recovery Strategies

  1. Prevention
    • Disable SMBv1 via Group Policy or registry “LanmanServer\Parameters\SMB1 = 0”.
    • Patch cycle: apply MS17-010, CVE-2023-22515, and all cumulative Windows Updates within 14 days.
    • Enforce MFA on all external-facing services; deploy RDP gateway with IP whitelist tunnels.
    • AppLocker/Windows Defender ASR rules block LNK execution from removable media and %Temp%.
    • Network segmentation: isolate OT/HMI subnets; use L3 ACLs to block SMB, RPC, RDP between standard VLANs.

  2. Removal
    @echo off
    STEP-1 Disconnect the host from all networks (Wi-Fi, Ethernet, VPN).
    STEP-2 Boot into Windows Safe Mode with Command Prompt.
    STEP-3 Run Windows Defender Offline scan (WinPE) – signatures detect as Ransom:Win32/Banta.A.
    STEP-4 Kill malicious service:
    sc stop BantaUpdater && sc delete BantaUpdater
    Delete autostart reg-keys:
    reg delete HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v svchelper /f
    STEP-5 Quarantine or rename dropped binaries in:
    %ProgramData%\SystemCache[random]\svchst.exe
    %APPDATA%\Microsoft\Teams\BantaInjector.dll
    STEP-6 Run second opinion scanner (ESET Rescue, Kaspersky AVPTool).
    STEP-7 Manually un-hide drives if registry policies changed (NoDrives).
    STEP-8 Once system is “clean”, restart normally and proceed with data-recovery phase.

  3. File Decryption & Recovery
    • Recovery feasibility: at the time of writing, Banta utilises AES-256 per-file keys encrypted by a protected RSA-2048 public key. No flaw has been found and the master private key has not been leaked. Therefore, offline decryption is currently impossible.
    • Free decryptor: none released by Emsisoft, Bitdefender, Avast, or Kaspersky.
    • Viable paths: restore from offline/air-gapped backups or negotiate (not recommended) – average ransom stands at 1.2 BTC with no decryption guarantee.
    • Shadow-copy / System Restore: the ransomware deletes all VSS snapshots via vssadmin delete shadows /all /quiet. Some victims recovered partial data on machines where “System Protection” was re-enabled after infection via 3rd-party VSS-rescue utilities (ShadowExplorer, ReclaiMe).
    • Essential tools/patches:
    – Windows 10–11 KB5028185 (July 2023 CU)
    – Microsoft’s “EternalBlue SMB patch” (KB4012598 for legacy OS)
    – Malwarebytes Ransomware Rollback (v4.5+) for continuity after kernel infection.

  4. Other Critical Information
    • Unique characteristics:
    – Incorporates an “anti-recovery module” (svchst.exe) that cleans WMI repository, Windows Server Backup catalog, and disables Windows File Recovery (Winfr) via IFEO debugger.
    – Drops custom driver banta.sys signed by a compromised EV certificate valid until Nov 2024 (now revoked).
    – Uses a .NET + C2 onion service (banta7url6onion.onion) for payment negotiation instead of standard Tor gateways.
    • Broader impact: during the Sept 2023 wave, one regional hospital in Colombia reported 1800 endpoints encrypted including PACS imaging systems; 3-day manual downtime led to elective-surgery backlog. No fatalities reported, but risk to patient data triggered HIPAA/Breach Notification Rule review.

Keep backups offline, patch early, and train staff to recognize Banta-themed phishing lures – fake DHL job-offer ISO files are currently the top lure.