abcd

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Exact Extension: .abcd

  • Renaming Convention:
    After encryption, files are left with a second extension in lower-case .abcd.
    – Original file: Invoice_2024-03.xlsx
    – After attack: Invoice_2024-03.xlsx.abcd

    In most observed samples it does not alter the base name or prepend with IDs/IDs-MACs, making it look “clean” compared with other families that add machine GUIDs or e-mail addresses.

2. Detection & Outbreak Timeline

  • Approximate Start Date: The first widespread samples tagged as “LockBit Black” while using the .abcd extension were captured and publicly shared on 2022-09-15 ±1 week.
    – .abcd is a variable extension option in the LockBit 3.0 (aka LockBit Black) builder; operators periodically change the annex extension.
    – Campaigns sporting .abcd increased sharply through November 2022-January 2023, and sporadic clusters continue to be seen through 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP / VNC brute-force & credential stuffing
    – Initial foothold via unprotected or poorly-hardened remote access (RDP → 3389, AnyDesk, TeamViewer).
  2. Phishing e-mails + drive-by downloads
    – Weaponized ISO or password-protected ZIP attachments containing staged Cobalt Strike or IcedID loaders.
  3. Exploitation of public-facing vulnerability
    – Known exploits:
    * Citrix NetScaler (CVE-2022-27518)
    * Fortinet FortiOS SSL-VPN (CVE-2022-42475)
    * Microsoft Exchange ProxyNotShell chaining (CVE-2022-41040 + CVE-2022-41082)
  4. Lateral movement via SMB
    – Post-breach, PoC versions deploy psExec, WMIC, or built-in Admin$ shares to push the payload laterally.
  5. DLL side-loading & signed-driver abuse
    – Uses legitimate executables (e.g., version.dll) and vulnerable but signed drivers (zam32.sys, aswArPots.sys) to kill AV/EDR before encryption.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    – Patch aggressively: Prioritize all CVEs listed above; enforce virtual patching via WAF/NIPS for external gateways.
    – Disable RDP or restrict via VPN + MFA + IP allow listing.
    – Disable or restrict Remote-Desktop-Service Protocol (RDS) user rights.
    – E-mail hygiene: Block ISO/IMG/VHD attachments at the gateway; sandbox macro Office documents.
    – Implement tiered admin model: Remove Domain-admin usage on workstations; apply LAPS and apply Privileged Access Workstations (PAWs).
    – Deploy application whitelisting / EDR solutions with signed-driver-tamper protection (CrowdStrike, SentinelOne, Microsoft 365 Defender – HVCI).
    – Backups 3-2-1 style: Immutable, off-site, tested weekly; lock down backup hosts with MFA.

2. Removal

  • Infection Cleanup (generic LockBit Black procedure):
  1. Isolate: Disconnect affected machines from LAN/Wi-Fi & VPN immediately.
  2. Boot from external media or use cloud-recovery: Launch into Safe Mode (Windows) or boot a live Linux USB with internet disabled.
  3. Kill persistence hooks: Check
    – HKLM\SYSTEM\CurrentControlSet\Services\ for malicious driver or service keys.
    – Scheduled tasks (schtasks /query /fo list /v) for .ps1, .vbs, or .exe under %APPDATA%.
    – Typical paths: %TEMP%, %PUBLIC%, C:\Perflogs, %SystemRoot%\system32\, reuse of %WinDir%\System32\svchost.exe.
  4. Update antivirus signatures or use standalone bootable AV (Kaspersky Rescue Disk, Windows Defender Offline) to quarantine identified files.
  5. Re-image OS drives for full confidence; preserve forensics on separate disk first if legal/compliance case.
  6. Reset all passwords in Active Directory after the last IOC timestamp, especially for any privileged accounts.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Impossible via decryption. LockBit 3.0 uses robust ChaCha20 + RSA-2048 hybrid cryptography; private keys remain on the attackers’ server.
    – No public decryptor exists for .abcd samples; ignore scam tools pretending to unlock them.
  • Essential Tools / Patches:
    – Bitdefender LockBitDecrypter – only valid for v1/2; NOT for Black v3 (.abcd).
    – Current official decryptor matrix: NoEmsisoft, Kaspersky, or Avast offerings support .abcd as of 2024-Q2.
    – Forensic shadow copies: Check Windows Volume Shadow Copies (vssadmin list shadowstorage / shadowcopyexplorer) – .abcd payload routinely deletes these, but some missed samples leave them intact.
    – If backups: Restore from off-line or WORM backups after verifying telemetry that timestamps precede the first encryption events.
    – File-carving is possible only for very specific file types and partial recovery from unencrypted slack space – low-percentage scenario.

4. Other Critical Information

  • Unique Characteristics:
    – LockBit 3.0 contains “Steal Bit” module that exfiltrates data prior to encryption; attack is not just ransomware but full double-extortion.
    – Affiliates choose the .abcd extension dynamically – the same build may also append .lockbit, .lock3, or Morphi. IOC checks must rely on ransom note filename (Restore-My-Files.txt / !!!_Restore_Files.txt) + artifacts, not on extension alone.
    – Self-spreading capabilities: The ransomware leverages markedly high-performance multi-threaded encryption and can run in safe-mode with networking to speed up disk wiping.
  • Broader Impact:
    – High-profile hits include industrial manufacturers, medical device firms, and a major Canadian hospital system (Sept-2023) resulting in 2-week patient-care disruption.
    – MITRE ATT&CK enterprise mapping:
    T1078 Valid Accounts, T1021.001 RDP, T1486 Data Encrypted for Impact, T1041 Exfiltration over C2.

Stay vigilant; treat every .abcd incident as a data-breach by default and engage incident-response + legal counsel specializing in privacy law immediately.