_locky_recover_instructions.txt

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .locky (sometimes written as .locky only; the ransom note is NOT the extension but accompanies every encrypted file set). Older campaigns have also been observed using .zepto, .odin, .thor, .aesir, .zzzzz, .shit, or .osiris, but all fall under the Locky family tree.
  • Renaming Convention:
    Plain files become a 36-character hexadecimal string + .locky (example: F04A47A0912E47B881BD429C8E8F5ED3.locky). Before encryption, Locky deletes Volume Shadow Copies (vssadmin delete shadows /all /quiet) and strips original filenames from NTFS MFT to hinder forensic reconstruction.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
  • First sighting: 16-Feb-2016 (Netherlands campaign that escalated globally within 48 h).
  • Peak waves: April 2016 (Dridex-powered spam blasts), September 2016 (.odin), January 2017 (.aesir), August 2017 (.ykcol), then sporadic flare-ups through 2018.
  • Since 2019 Locky has largely disappeared from the wild (superseded by Sodinokibi, Maze, Conti), but dormant C2 panels and samples still surface in honeypots and “archived” malware kits.

3. Primary Attack Vectors

  1. Malicious Office macros – e-mail phishing (“invoice”, “payment”, “voicemail”) that downloads Locky payload from remote C2 using PowerShell.
  2. Exploit kits (EITest, Nuclear, RIG) served via compromised ad-networks.
  3. RDP brute force → living-off-the-land PSExec/WMI lateral movement inside corporate networks (especially in 2018 LNK campaigns that delivered Zepto).
  4. Samba/SMBv1 exploitation in very early samples leveraging the same pipeline as Dridex, but not a primary vector long-term.
  5. WSF/JS/VBS e-mail attachments disguised as .zip files.

Remediation & Recovery Strategies:

1. Prevention

  • Disable Office macros by default or globally via Group Policy (GPO).
  • E-mail filtering: Block top-level attachments: .wsf, .js, .jse, .vbe, .wmf.
  • Patch Windows & disable obsolete SMBv1; enforce MFA on VPN/RDP endpoints.
  • Backup 3-2-1 strategy: 3 copies, 2 media types (immutable cloud, off-site tape), 1 offline/air-gapped. Enable WORM or versioning to stop attackers deleting backups.
  • Application whitelisting/AppLocker to stop unknown binaries in %APPDATA% & %TEMP%.
  • Egress filtering: Deny outbound TCP 80/443 traffic from non-browser processes via firewall to neuter initial C2.

2. Removal

  1. Disconnect from network (RJ-45, Wi-Fi, Bluetooth).
  2. Boot into Safe Mode with Networking OFF.
  3. Run Trend Micro Ransomware File Decryptor (for offline analysis only), Malwarebytes, MSERT, or ESET Online Scanner.
  4. Remove malicious scheduled task (rundl32.exe \Windows\system32\d3d10.dll,DTGetCacheEntry) and registry run key (HKLM/HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\Locky).
  5. Observe DNS logs for fallback domains (.top, .ru, .com) and blacklist them.
  6. Change ALL passwords (admin, service accounts, stored browser vaults) once cleaned.
  7. Patch and harden (see “Prevention”) before reconnecting machines to domain.

3. File Decryption & Recovery

  • Possibility of Decrypting: Not feasible for original .locky samples.
    The payload uses AES-128 file keys → RSA-2048 offline master public key; private key resides only with the actor. No public decryptor exists for the mainstream 2016-2018 campaigns; sweeping “LockyDecryptor” scams were red herrings.
  • Minor exceptions:
  • Very early pre-.locky test variant (Feb 2016; sample hash 57b7…0e1a) used weak PRNG; Avast & Nanny State released an automated decryptor.
  • Victims who captured the C2 session key file (.lukitus version) kept it before ransom note generation had one or two successful co-operative decryptions (still not available publicly).
  • ShadowExplorer / carved VSS may restore previous versions if snapshots were disabled AFTER first infection; worth forensic scan with ShadowCopyView.
  • Recommended Tools:
  • SolarWinds Restore Point Scanner, ReclaiMe File Recovery for Volume Shadow Copy Sectors.
  • Microsoft’s Disaster-Recovery-as-a-Service (Azure Site Recovery) for large orgs corporate roll-back points.
  • STOP/Djvu Decryptor ≠ Locky – do not attempt unless lineage confirmed.

4. Other Critical Information

  • Unique Characteristics:
  • Multiple spin-offs (.odin, .zepto, .aesir) but same payment BTC addresses rotate; threat group rebrands every few months to evade takedown & reimbursement tracking.
  • The gang leverages Dridex banking-trojan network infrastructure; infected PCs were pre-staged for Locky mass spam blasts.
  • Message header language localised (L10N) to victim’s geolocation at send-time using e-mail harvesting from LinkedIn & Jigsaw.
  • Wider Impact:
  • Hollywood Presbyterian Medical Center (California) paid 40 BTC (~USD 17k at time) in Feb-2016—sparked U.S. Senate hearings on medical ransomware.
  • Peak daily revenue estimated 200-400 BTC at height of outbreak (Chainalysis report Q2-2016).
  • GMT campaign (Aug 2016) with 7.5 M messages blocked in 30 min by Microsoft SmartScreen due to scale.
  • FBI/Trend Micro sinkholing some C2 in June 2016, but operators moved infrastructure faster than takedowns—illustrated modern Raccine-resistant techniques now copied by newer families.

By following the prevention checklist—macro policy, e-mail hygiene, network segmentation, MFA, and tested offline backups—you render Locky practically harmless, even if the payload resurfaces tomorrow via a new disguise.