bianlian

[Content by Gemini 2.5]

Technical Breakdown: BianLian (.bianlian)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by BianLian receive the literal suffix .bianlian appended to each affected file.
  • Renaming Convention:
    OriginalFileName.ext.bianlian
    Example: 2024_Report.xlsx becomes 2024_Report.xlsx.bianlian.
    The malware removes any previous backup / Windows “previous versions” shadow-copy references, so the extension appears as the final 9 visible bytes of every encrypted object.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First documented clusters appeared in August 2022, with rapid expansion observed globally during Q4 2022 – Q2 2023.
    Threat-intel telemetry shows monthly spikes in March, May, and November 2023, indicating active affiliate campaigns and code rebases.

3. Primary Attack Vectors

  • Remote Desktop Protocol (RDP) & VPN Exploits – Mass scanning for RDP (3389), SSH (22), and common VPN appliances (Fortinet, SonicWall, Ivanti) followed by credential stuffing or key “password-spraying.”
  • Remote Management Tools – Legitimate applications such as AnyDesk, Atera, and GoTo Resolve are installed or hijacked post-breach to maintain persistence and pivot laterally.
  • Software & OS Vulnerabilities – Rapid exploitation (often < 24 h from patch release) of critical bugs like:
  • CVE-2022-40684 (FortiOS/FortiProxy auth-bypass)
  • CVE-2023-27350 (PaperCut NG/MF)
  • CVE-2023-34362 (MOVEit Transfer / CVE-2023-35036 follow-up)
  • Phishing with HTA / ISO attachments (less frequent than RDP route) delivering PowerShell or Go-based loaders that then download the core encryptor.

Remediation & Recovery Strategies:

1. Prevention

  • Lock Down RDP – Restrict RDP to VPN only, enable NLA, disable 3389 on WAN, enforce strong accounts policies, deploy MFA on privileged access (jump boxes or PAM).
  • Patch Cycle (N-0, not N-7) – Apply “critical” and “known-exploited” patches as soon as vendor releases, not monthly. Public POCs for CVE-2023-34362, 2022-40684, etc., dropped within hours.
  • Network Segmentation & Zero-Trust – Isolate backup networks; deny lateral SMB/RDP traversal via VLAN ACLs and local-firewall rules.
  • WAF / IPS Signatures – Ensure FortiGate, Palo Alto, or Snort rules are up to date for credential-stuffing and VPN exploit patterns.
  • Deploy EDR/NGAV with behavioral blocking – Signature alone is insufficient; monitor for:
  1. Large-scale file-move rates,
  2. Kernel-handle duplication fuzzing,
  3. curl/wget to onion domains.

2. Removal

  1. Isolate Immediately – Physically pull network cables / disable Wi-Fi to stop exfil & final wipe scripts.
  2. Determine Compromise Scope – Review Sysmon/EDR for
  • powershell.exe -ExecutionPolicy Bypass,
  • Naming patterns like mysqldump.exe.bianlian,
  • TOR EXEs under %Temp%.
  1. Kill & Delete Persistent Mechanisms
  • Scheduled tasks: schtasks /query /fo csv | findstr bianlian /i
  • Registry: HKLM\Software\Microsoft\Windows\CurrentVersion\Run values that call .tmp.exe Go binaries.
  1. Wipe OS Layer Where Able – Full re-image is strongly recommended; bootkits are rare but root certificates have been observed tampered.
  2. Patch & Rebuild – Apply latest OS patch roll-ups and harden local firewall (see Prevention section) before reconnecting to domain.

3. File Decryption & Recovery

  • Recovery Feasibility: NO reliable free decryptor currently available. Crypto is AES-256 with per-file salts plus RSA-2048 public key, stored server-side.
  • What Works:
  • Offline backups: The only guaranteed path.
  • Volume Shadow Copy Recovery: Usually wiped via vssadmin delete shadows /all /quiet. Salvage may be possible if malware crashed early.
  • Essential Tools/Patches to Avert Loss:
  • Veeam, Commvault, or other backup products with immutable vaults (S3 Object Lock, Crypto-Lock).
  • SentinelOne, CrowdStrike, or Microsoft Defender for Endpoint with “rollback”/“auto-isolate” enabled.
  • Enable BitLocker with TPM so the OS itself remains encrypted (reduces token theft likelihood).

4. Other Critical Information

  • Double-Extortion Tactic: Data is exfiltrated via MEGA, Filemail, FTP, or rsync with onion-proxy prior to encryption. Victims often receive a live-chat page (Tor) threatening leak unless payment occurs within 5–7 days.
  • Go-Based Cross-Platform Core: The encryptor is built in Go; Linux petabyte-scale NAS or VM stores have been targeted.
  • Proxyshell & PrintNightmare families – Initial comms port 8000 to gather domain hashes, similar to BlackCat/ALPHV.
  • Kill-Date: Samples set a kill-switch date (SHA256:941e3…) that unconditionally terminates after January 1, 2025 — do not rely on it for infection-control.

TL;DR Action Plan

  1. If currently infected: Power-off, sever all links, engage incident-response; don’t pay — decryption is not assured and double-extortion may still result in a leak.
  2. If you are protected: Migrate backups to S3-Immutable or WORM tape today; patch VPN/RDP today; review firewall ACLs blocking 3389/22 inbound.

Stay vigilant; BianLian is rapidly evolving and affiliates frequently recompile.