bitcrypt 2.0

[Content by Gemini 2.5]

Technical Breakdown: bitcrypt 2.0 (.bitcrypt2)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: All encrypted files receive the suffix .bitcrypt2 appended after the original file extension. Example: report.xlsx becomes report.xlsx.bitcrypt2.
  • Renaming Convention: Files are not renamed in any other way—names, paths, and timestamps remain unchanged once encrypted. Victims often report that only the extra four-megabyte footer injected by the malware indicates a file has been altered beyond the new extension.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: BitCrypt 2.0 was first observed and documented in underground Russian-language forums in early January 2023, followed by a sharp spike in detections by commercial EDR telemetry in mid-March 2023. Mass-replication campaigns peaked in April-May 2023.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Exposed RDP ports (TCP 3389) brute-forced with common username–password lists using the “Golden Chick” credential-stuffer pack.
  2. QakBot (Qbot) loader – phishing e-mails with ISO or OneNote attachments deliver QakBot, which spawns Cobalt Strike beacon traffic and ultimately drops netsh-routed bitcrypt 2.0 binaries.
  3. ProxyLogon Exchange exploit (CVE-2021-26855 + 26857 chaining) still widely unpatched on EOL 2013/2016 servers.
  4. Legacy SMBv1/EternalBlue deployment bundle deployed via WMI for lateral movement once initial foothold is secured.
  5. MSP / RMM tool abuse – more recent campaigns (late 2023) compromise N-able, AnyDesk, or TeamViewer tokens to push MSI or macro-laden documents en masse.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    – Disable SMBv1 completely (Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol or GPO).
    – Restrict RDP (TCP 3389) to a jump host behind VPN; enforce MFA + NLA + account lockout (3-5 failures / 30-minute window).
    – Patch Windows, Exchange (ProxyLogon & ProxyShell), Fortinet, Citrix ADC, and any VPN gateways immediately.
    – E-mail gateway blocking of ISO/IMG, OneNote, and macro-enabled Office files.
    – Application-control (AppLocker, WDAC) to prevent unsigned C2 binaries such as nsr.exe, wininit_client.exe, and bc2_cfg.dat from executing.
    – Application whitelisting of MSP/RMM agents to prevent rogue command lines.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Isolate – Physically disconnect network or enforce “Quarantine VLAN” via NAC / switch ACL.
  2. End processes – Identify and kill bc2.exe, nsr.exe, wininit_client.exe (names rotate per campaign) using Task Manager/Process Explorer or EDR quarantine action.
  3. Delete persistence – Remove scheduled tasks named MicrosoftUpdateBC2 or registry run keys in HKCU/HKLM\Software\Microsoft\Windows\CurrentVersion\RunOnceEx\99.
  4. Clear WMI event subscriptions used for lateral movement (wmic /NAMESPACE:\\root\subscription PATH __EventFilter DELETE /WHERE Name="EventConsumer_Bc2").
  5. Re-image vs. clean? – Once lateral movement is confirmed or Cobalt Strike beacons established, prioritize full OS re-imaging from known-good baseline or VHD; then restore data from offline backups only.

3. File Decryption & Recovery

  • Recovery Feasibility: BitCrypt 2.0 uses ChaCha20-Poly1305 per-file keys, wrapped by an EC-secp256k1 public key stored inside the .bitcrypt2 footer. Brute-force or key-leak possibilities are currently nil.
    – Limited success rate: investigators have recovered encryption keys only for victims hit in April 2023 campaigns due to a memory-image snapshot containing the unpacked private key. Key material has since been rotated in May 2023 and again in November 2023 updates.
    – No official decryptor exists.
    – Best Remedy: meticulous off-line backups or roll back to pre-infection immutable snapshots (Object-Lock S3, immutable Veeam repo, ZFS snapshots with syncoid + --no-sync-snap).

4. Other Critical Information

  • Unique Characteristics:
    – Targeted exfiltration via MEGA.nz encrypted shares before encryption—you will notice large outbound transfers even if files remain on-disk. Always assume data has leaked.
    – Dark-web leak site posts victim IDs within 72 h if ransom unpaid.
    – AI-taunt message replacing desktop wallpaper with South Park-style caricatures of the victim’s organization—used in about 35 % of incidents to increase psychological pressure.
  • Broader Impact:
    – High casualty rate among hospitals & clinics (EMR downtime, postponed surgeries).
    – Partial compromise of multifunction printers to steal scan-to-email credentials—unusual in this family.
    – State & federal incident response advisories now combine BitCrypt 2.0 with Diamond-Fluorine ransomware affiliate program. Treat each case as both ransomware + extortion + possible APT.

Bottom Line: Because BitCrypt 2.0 is primarily a post-exploitation payload, focus on hardening RDP/SMB, Exchange, and third-party MSP tooling. If hit, assume exfiltration rather than encryption is the bigger damage vector; do not pay the ransom because decryptor reliability after May 2023 is near zero.