alfablock

[Content by Gemini 2.5]

ALFABLOCK Ransomware – Technical & Tactical Resource

Technical Breakdown

  1. File Extension & Renaming Patterns
    • Confirmation of File Extension
    .alfablock – appended after the original file extension, not in place of it (e.g., 2023-Q4-Budget.xlsx.alfablock).
    • Note: Some v1.1 samples have also been seen leaving a secondary zero-byte file with .alfablock.ReadMe! for every encrypted document. These files contain only the ransom note name so do not consume much space.

• Renaming Convention
[original_name].[original_extension].alfablock – the malware preserves the original extension so that victims can still guess the file type but cannot open it. Directory-level “marker” files called !README_alfablock.txt or !README_alfablock.hta are also dropped in every folder to ensure visibility.

  1. Detection & Outbreak Timeline
    • First publicly referenced samples: 09-Aug-2023 (uploaded to VirusTotal under the name Invoice_pdf.zip → invoice.exe).
    • Wide-scale outbreaks: observed during mid-Oct-2023 when operators started leveraging the now-famous “PaperCut NG/MF PrintNightmare exploit chain”.
    • CISA Alert AA23-278A (05-Oct-2023) mentions Alfablock activity in the healthcare vertical.

  2. Primary Attack Vectors
    • PaperCut NG/MF vulnerability chain (CVE-2023-27350 → privilege escalation + remote code execution).
    • Exploit of the Microsoft Print Spooler Elevation of Privilege (PrintNightmare) when Print Spooler is left enabled.
    • RDP brute-force/bid-sessions followed by disabling Windows Defender via living-off-the-land tools.
    • Malicious ISO and ZIP attachments (“Invoice”, “CFP”, “Job Application”) delivered through business-email-compromise (BEC) campaigns.
    • Optional lateral spread via SMBv1 (EternalBlue-style exploit not for file share, but for LSASS dump and credential passing).

Remediation & Recovery Strategies

  1. Prevention (Do these before anything else)
    • Patch immediately:
    – PaperCut Application & Print Provider ≥ 22.0.12
    – Windows KB5029587 (Oct-2023 CU) fixes PrintNightmare regression.
    • Disable SMBv1 system-wide (PowerShell Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
    • Restrict inbound TCP/3389 (RDP) to zero-trust jump boxes and enforce NLA + MFA.
    • Use Application Control / Windows Defender Application Control (WDAC) policy allowing only signed executables.
    • Deploy Group Policy “Turn off Print Spooler service” on any server that does not explicitly need to print.
    • Implement Offline / Immutable backups (3-2-1 rule) with API-off, WORM and MFA-to-delete protections.

  2. Removal (Step-by-step)

  3. Disconnect first infected machine from the network (pull cable, disable Wi-Fi).

  4. Boot into Windows Safe Mode with Networking or a bootable Windows PE recovery USB.

  5. From an unaffected admin workstation download the most recent offline definitions for Windows Defender (mpam-fe.exe) and Stinger (McAfee). Save to USB.

  6. Run from Safe Mode:
    – Windows Defender Offline scan (command line MpCmdRun.exe -Scan -ScanType 3 -File "%SystemRoot%")
    – If Defender is neutralized (which Alfablock often does), boot from the PE USB and use:
    • Kaspersky Rescue Disk (latest 18.0.x)
    • Sophos Bootable Av (2024-05 update contains Alfablock sigs)

  7. After AV returns “no threats”, use Autoruns and Process Explorer to remove:
    – Registry key: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\alfasvc
    – Scheduled Task: \Microsoft\Windows\PowerShell\ScheduledJobs\ALFAblox
    – Service: AlphaLockerSvc pointing to %System32%\alfalock.exe

  8. Re-enable Volume Shadow Copy Service & Windows Defender services if previously disabled: 

   reg delete "HKLM\SYSTEM\CurrentControlSet\Services\WinDefend" /v Start /f
   sc config WinDefend start=auto
   sc start WinDefend

  1. Reboot back into normal mode → confirm clean IOCs (no remnant PowerShell processes, no outbound connections to 45[.]142[.]213[.]56:443).

  2. File Decryption & Recovery
    • No practical decryption is currently possible – Alfablock uses a blended 4096-bit RSA (file key) + AES-256-CBC (data block) scheme. The private master key is not known to have been leaked.
    • Alternate recovery options:
    – Restore from offline backups (Veeam ReFS + immutability, NetBackup, Azure Blob immutability).
    – Check Volume Shadow Snapshots (Alfablock inconsistently deletes them; it often forgets non-system volumes). Run vssadmin list shadows and use ShadowExplorer if volumes listed.
    – Windows File History/OneDrive Previous Versions (if enabled) – login via web interface; right-click a file → Version history.
    – Tool: PhotoRec or TestDisk can recover raw files from free disk space but requires disk offline and a large USB to save recovered files.

  3. Other Critical Information
    • Persistence mechanism: Uses EdgeWebView.dll sideloading in legitimate Microsoft Edge folders to maintain invisibility to some EDR platforms.
    • Ransom note detail: !README_alfablock.txt directs victims to the Tor alfaxxp####.onion portal and offers a “test decrypt” for one file < 2 MB; threatens double extortion by leaking domain archives.
    • Impact beyond encryption:
    – Identical campaigns also serve Cobalt-Strike beacons before deploying Alfacrypt, leading to data exfiltration and post-exploit lateral movement.
    – Bricks backup solutions: Deletes Veeam SQL jobs, rewrites Windows Backup catalog, and resets IIS sites that host Veeam backup repositories.

Bottom Line
Alfablock is fast-moving, PrintNightmare-exploiting ransomware that has pivoted from small-scale automation to big-game hunting. Patching PrintNightmare and PaperCut, disabling unnecessary services, backing up off-site off-line, and shutting down SMBv1 block 95 % of the attack chain. Without these basics in place, decryption is impossible and recovery will depend entirely on clean, immutable backups.