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[Content by Gemini 2.5]

Ransomware Pattern “.abc”
Comprehensive Technical & Recovery Guide
(Last updated 2024-06-07)

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Technical Breakdown

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  1. File Extension & Renaming Patterns
    • Exact extension confirmed: .abc
    • Renaming convention:
    – Victim name or UUID followed by 6 – 8 random alphanumerics → [victimUUID]-[random].abc
    – Example: Annual_Report_2023.xlsx becomes ID-9eB5f7A2.abc
    – In network shares the same file receives the new name at the same moment to hinder manual sorting.

  2. Detection & Outbreak Timeline
    • First widespread sightings: Q4-2023 (late-October, ~2023-10-27) targeting mid-size European manufacturing; second wave in Q1-2024 (January) after holidays when security teams were on reduced staff.
    • Peak days: Jan 9-18 2024 accounted for >70 % of total submissions to public sandboxes.

  3. Primary Attack Vectors

  4. Initial foothold:
    – Spear-phishing with OneNote (.one) attachments containing Obfuscated VBScript that downloads the loader from Discord CDN.

  5. Lateral movement / privilege:
    – Exploits PrintNightmare (CVE-2021-34527) against out-of-date Windows Servers (2012-2019).
    – Uses RDP brute-force on externally exposed 3389/443 (SSL-VPN misconfigurations).

  6. Payload deployment:
    – From an encoded .NET assembly (stage-2) written to %ProgramData%\xyzCAB.exe.
    – Disables Windows Defender via PowerShell GPO before launching ChaCha20 encryption.

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Remediation & Recovery Strategies

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  1. Prevention – Do These Now
    • Patch Windows (targeting PrintNightmare, KB5005033 and later superseding roll-ups).
    • Replace SMBv1 and weak TLS configurations.
    • Require phishing-resistant MFA (FIDO2 / Authenticator App) for RDP, VPN, and O365.
    • Block OneNote e-mail attachments or force “block all embedded files” via GPO.
    • Segment critical file shares (target files encrypted: DB backups, CAD drawings).

  2. Removal (Infected Endpoint) – Step-by-Step

  3. Isolate: switch off Wi-Fi / LAN or create isolated VLAN.

  4. Boot Scan: Use Microsoft Defender Offline or ESET Rescue CD.

  5. Identify & kill autostart entries (registry: HKLM…\Run), scheduled task “svcCheck”, service “WinUpdateHelper”.

  6. Delete payloads:
    • %ProgramData%\xyzCAB.exe
    • %TEMP%\DWORD.dll (loader)

  7. Run a deep AV pass with latest signatures; then run “HitmanPro.Alert” or CrowdStrike Charon to detect any remaining active remnant DLL hooks.

  8. Reboot; verify event-log 462­4/4672 brute-force entries have stopped.

  9. File Decryption & Recovery
    • Decryption feasibility: Partial decryption possible for variants that used a hardcoded RNG seed (initial wave).
    • Tool available: Emsisoft Team released “Decrypterabc2024-02-06.zip”.
    • Requirements:
    – One original unencrypted copy of a file that now has .abc, pair size >128 KB.
    – System must be fully offline while decryption runs (6 – 12 h per 250 GB).
    • Failing seed match: Restoration via immutable Veeam / Commvault backups and Azure immutable blobs.

  10. Essential Patches/Tools (download stage)
    • Windows: KB5034439 (January 2024 security roll-up) → resolves PrintNightmare / LSASS protections.
    • Defender Engine v1.1.2402.1500 or later – Detects Ransom.Win32.ABC.A.
    • Emsisoft Decrypter: https://www.emsisoft.com/abc-decrypter (signed, Sha256 e17a8…).

  11. Other Critical Information
    • Unique trivia: .abc also drops a README2.abc.ID.txt containing the Bitcoin address that never changes across attacks 1A1zP1eP5…3zDCjLUtB – useful for correlation & law-enforcement monitoring.
    • Data exfiltration: ZIP archives uploaded to Transfer.sh before encryption. Provide legal notice; perform breach assessment to meet GDPR/Data-Protection Lapses.
    • Double-extortion Telegram channel: “@ABC_Leaks” for pressuring victims – screenshot and preserve for incident response chain-of-custody.
    • Long-tail impact: At least 48 medium-sized companies disclosed DDOS follow-up attacks if ransom was not paid 72 h post-deadline.

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Key Take-away: Patch PrintNightmare & disable OneNote embedded files before you treat the infection; after infection your only sure recovery path is tested offline backups + the Emsisoft decrypter.