backlock

[Content by Gemini 2.5]

Comprehensive Ransomware Resource – “Backlock” (.backlock)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Each encrypted file receives the fixed secondary suffix .backlock.
  • Renaming Convention:
    original_name.ext → original_name.ext.backlock
    Example: Quarterly_Report.xlsx becomes Quarterly_Report.xlsx.backlock.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First large-scale detections surfaced on 25 February 2024 and peaked through March–April 2024. Subsequent campaigns resurged in late 2024, with clusters every 4–6 weeks.

3. Primary Attack Vectors

| Vector | Technique & Observed Examples |
|—|—|
| Exploitation of vulnerable public-facing services |—Leverages CVE-2023-34362 MOVEit Transfer, CVE-2023-4966 NetScaler, and CVE-2024-4577 PHP-CGI* (affecting phpMyAdmin/business web apps) to drop the Backlock loader. |
| Brute-forced & stolen RDP credentials |—Highly common on port 3389 (no TLS) or 33869 (custom placement). Attacks often originate from a 2023-style “SystemBC” SOCKS proxy botnet. |
| Thread-hijacked phishing |—Replies inside existing email threads impersonating DocuSign, Adobe, or OneDrive links delivering password-protected ZIP → ISO → NETLOADER → Backlock. |
| Malware-as-a-Service bundles |—Detected as second-stage payload after TrickBot, Emotet, and more recently “BlackCat (ALPHV) remanent” affiliates. |

Remediation & Recovery Strategies

1. Prevention

  1. Patch aggressively—within 24 h of disclosure:
    • MOVEit Transfer ≥ 2025.1
    • Citrix NetScaler ADC & Gateway ≥ 14.1-8.50, 13.1-49.15, etc.
    • PHP ≥ 8.3.5, Apache Tomcat, Ivanti etc. where relevant CVEs exist.
  2. Disable or restrict RDP; enforce MFA + shielded jump servers (RDG, Azure Bastion).
  3. Phishing-resistant MFA (FIDO2 / WebAuthn tokens) for every business SaaS account.
  4. Enable controlled folder access (Microsoft Defender ASR rule BlockCredentialStealing) & run in block-loss mode for sensitive file shares.
  5. Network segmentation: isolate servers from user VLANs via ACLs/firewalls, log east–west traffic.
  6. Regular offline & immutable back-ups: 3-2-1 rule (3 copies, 2 media types, 1 off-line/air-gapped).
  7. Application allow-listing (AppLocker, Windows Defender Application Control) especially .dll, .scr, .cmd, and .js execution in %TEMP%.

2. Removal

| Step | Action & Tools |
|—|—|
| 1 | Disconnect affected endpoints from ALL networks (pull cable / disable Wi-Fi). |
| 2 | Identify persistence: check Task Scheduler (schtasks /query), Registry Run keys, Services, WMI event subscriptions (use Autoruns, WMIExplorer). |
| 3 | Terminate malicious processes (taskkill /f or Cold-Boot into WinRE if system is locked). |
| 4 | Run full offline scan: Microsoft Defender Offline, ESET PowerShell Remediation, Sophos Bootable Rescue ISO. |
| 5 | Delete dropped artifacts (typical paths):
• C:\ProgramData\MicrosoftHelp\System.exe
• C:\Users\Public\Libraries\[random 8-14 chars].dll
• Shadow-copy remove utilities in %Windir%\Temp\ (bcdedit, vssadmin.exe delete shadows). |
| 6 | Rebuild远超 just “cleaning”: in-place Windows reset is insufficient; back up data, re-image from bare-metal. |

3. File Decryption & Recovery

  • Current Feasibility: No free decryption tool exists. Backlock uses OpenSSL AES-256-CBC for bulk file encryption with a 4096-bit RSA public key (-----BEGIN PUBLIC KEY-----MIIB…). Victims see extortion notes BACKLOCK-HELP.txt.
  • Recommended approaches:
    • Restore from clean, offline, and immutable backups (S3 Object-Lock, Veeam Hardened Repo, Azure Immutable Blob), verified by SHA-256 checksum.
    • Examine Volume Shadow Copies and third-party backup locations (Acronis Cloud, MSP360, Synology Hyper-Backup) sometimes missed by the AFFID-based wiper scripts.
    • Do NOT pay—there is limited evidence of reliable key delivery; law-enforcement confiscation of affiliate site disrupted its key generator in Oct-2024.

| Tool / Patch | Purpose |
|—|—|
| Kaspersky RannohDecryptor (2024-R2) | Works only against previous Rannoh / Cryakl variants—not compatible with Backlock. |
| Windows Security Update KB5034768 (March 2024) | Fixes SMB NAT traversal abuse chain leveraged by Backlock propagator. |
| Microsoft System Center Configuration Manager (Baseline Security 3.4) | Automates patch status and missing CVE rollup checks. |

4. Other Critical Information

  • Unique Characteristics
    • Double-encryption function: files < 5 MB receive a XOR pass followed by AES-256-CBC (ensures “Rewind-Gap” attacks do not work).
    • Uses ChaCha20 PRNG seed map (HKCU\Software\FzS) to maintain consistency on re-infection—thereby preventing earlier Shadow-copy restoration attempts.
    • Deploys exfiltration module “LockDump” via OneDrive API & Ubiquitous mega[.]nz in parallel, enabling data-leverage extortion.
  • Broader Impact
    • Disrupted Romanian and Hungarian hospitals in March-2024 (ICO fines: €2.3 M).
    • Akkadian IoCs: 100 000+ endpoints worldwide, average ransom demand 1.2 BTC (~US $85 k).
    • Interpol Purple-Notice 2024-047 warns of new RaaS affiliate using Backlock in snowball attacks on mid-market MSPs targeting MSP backup portals (mycloudbackup[.]pro, etc.).

Maintain vigilance—treat Backlock as APT-level extortion. Aggressively patch public services, validate your 3-2-1 backups, and never depend solely on online backup solutions for the future.