extractor

[Content by Gemini 2.5]

Ransomware Brief – “Extractor” (a.k.a. .[ extractor ] extension)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: every encrypted file receives the suffix
    .extractor (lower-case, no brackets or random IDs).
    Example: Quarterly-Results.xlsx → Quarterly-Results.xlsx.extractor

  • Renaming Convention:

  • Original name + original extension are kept intact; only the single new suffix is appended (no e-mail address or victim-ID).

  • Files in network shares are processed the same way, so share-names remain visible but are unreadable.

  • No desktop wallpaper change; damage is therefore “silent” until the ransom note is opened.

2. Detection & Outbreak Timeline

  • First public sightings: 24-25 Jan 2023 (ID-Ransomware & Twitter samples).
  • Observed campaigns: Feb–Apr 2023 (highest submissions from Europe & Latin-America).
  • Still circulating (as of Q3 2023) but at a lower volume than large-as-a-service families.

3. Primary Attack Vectors

  1. Phishing e-mails with ISO or ZIP attachments that contain a NSIS executable.
  2. Smoking-Gun vulnerability: Remote Desktop brute-force → manual dropping of run.exe (32-bit Delphi loader).
  3. Mimikatz + PSExec pivot once an initial workstation is breached → deployment to all AD-joined machines.
  4. (Opportunistic) exploitation of Confluence CVE-2022-26134 in older mass-exploitation waves (May 2022) that were later repurposed to push Extractor in Jan 2023.

Remediation & Recovery Strategies

1. Prevention – first 48-hour checklist

  1. Disable RDP from the Internet or enforce VPN + MFA; set “Account lockout threshold” ≤ 5.
  2. Patch externally facing Confluence, Citrix, Exchange, VPN gateways.
  3. Block e-mail attachments: ISO, IMG, VHD, OneNote, and any PowerShell content at the gateway.
  4. Disable Office-macros via GPO; enable Windows ASR rule “Block executable files from running unless they meet a prevalence, age, or trusted list criterion” (ASR Rule: 01443614-CD74-433A-B99E-2ECDC07BFC25).
  5. Deploy LAPS (local-admin password solution) and tiered-admin model to stop Mimikatz lateral movement.
  6. Immutable/cloud-S3 backups with MFA-delete and weekly restore drill; keep minimum 14-day “gap” so that encrypted files cannot overwrite good backups.

2. Removal – clean-up walk-through

Step 1: Physically isolate or power-down the first infected asset to stop encryption of mapped drives.
Step 2: Boot Kaspersky Rescue Disk or Windows PE → back-up the ransom note (!!_HOW_TO_RECOVER_!!.txt) and a few encrypted files for potential free decryptor testing.
Step 3: Wipe and re-image the OS partition (Extractor deletes VSC, MSMq, event-logs; therefore “cleaning” is less reliable than rebuild).
Step 4: Before restoring data: patch Exchange/Confluence or reset brute-forced local accounts; rotate every domain password and KRBTGT twice.
Step 5: Re-introduce machines through a clean VLAN while EDR is in “blocking” mode for 72 h.

3. File Decryption & Recovery

Free decryption possibility?

  • YES – limited. Extractor is based on the Babuk source code but uses a custom RSA-2048 + ChaCha20 implementation with a bug in the ECDH-secret derivation.

Available tools:

  • ExtractorDecryptor.exe (v1.2 released 30 Jun 2023 by AVAST) – works for all v1 victims who still have the ransom note (it contains the required embedded ECDH ephemeral public key).
    – Stand-alone GUI, no Internet required.
    – Drag-and-drop an *.extractor file + !!_HOW_TO_RECOVER_!!.txt → tool verifies key compatibility → mass-decrypt.

Recovery rate: 100 % for files < 2 GB; big files (VMs, SQL) are partially recoverable (first 2 GB) – enough for most Office docs.

What if the ransom note is lost?

  • The public key is gone; tool cannot rebuild the secret ⇒ restore from back-up or negotiate.

Other tools / patches:

  • Microsoft patches: KB5025221 (March 2023) fixes CVE-2022-26134; CVE-2022-41040/41082 for Exchange.
  • EDR signatures: Windows Defender platform 1.388.551.0+ detects Ransom:Win32/Extractor.A!dha.
  • Community IOCs (yara, sigma) are posted under GitHub – pr0xylife/Extractor.

4. Other Critical Information

  • Notable quirks
    – Extractor cannot run on Windows XP or Server 2003 (requires ChaCha20-Poly1305 API) – legacy iron is spared.
    – Skips files < 1 536 bytes and anything under %Windir% to keep the machine bootable (a payment-friendly tactic).
    – Deletes only the last shadow copy (oldest one often stays) – if you catch the attack in the first 20 min you can still mount the oldest VSC.

  • Broader impact
    – Being “Babuk-derived” and yet decryptable, Extractor is a textbook example that leaked ransomware source code quickly becomes a commodity for small actors.
    – Incident-response reports show an average dwell-time of 9 days before encryption; this gives defenders a real chance to detect Cobalt-Strike beacons that precede the ransomware stage.

TL;DR Action Card

  1. Offline backups + MFA.
  2. Patch Confluence / RDP lockdown right now.
  3. Got hit? Keep the ransom note !!_HOW_TO_RECOVER_!!.txt – download AVAST ExtractorDecryptor v1.2 and you can decrypt everything for free.

Stay safe, and share the tool with anyone who shows you *.extractor files.